HEWITT ASSOCIATES INCFiled by

AON PLC

FORM 425(Filing of certain prospectuses and communications in connection with business combination transactions)

Filed 09/01/10

CIK 0001168478

SIC Code 6411 - Insurance Agents, Brokers, and ServiceIndustry Insurance (Miscellaneous)

Sector FinancialFiscal Year 09/30

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Distribution and use of this document restricted under EDGAR Online, Inc. Terms of Use.

Filed by Aon Corporation

Pursuant to Rule 425 under the Securities Act of 1933 and deemed filed pursuant to Rule 14a-12 under the Securities Exchange Act of 1934

Subject Company: Hewitt Associates, Inc.

Commission File No.: 001-31351

Commission File No. for Registration Statement on Form S-4: 333-168320

This document was posted by Aon Corporation on its integration portal accessible on its internal website on September 1, 2010.

The Joini ng of Aon and Hewitt Creating the Global Leader in Human Capita l Solutions September 2010

This communica tion contains certain statements rela ted to future results, or sta tes our intentions, beli efs and expec tati ons or predicti ons for the fut ure which are forward-looking sta tements as that t erm is de fi ned in the Pri va te S ecuriti es Lit igation Re form Ac t of 1995. These forward-looking sta tements are subjec t to certa in risks and uncertainti es tha t could cause ac tual resul ts to differ ma ter ia lly from eithe r histor ica l or antic ipated resul ts depending on a va ri ety of fac tors. Potentia l fact ors that could impact resul ts include : the possibi lity that the expec ted effic ienc ies and cost savings from the proposed transact ion w ill not be realized, or will not be realized w ithin the expec ted time pe ri od; t he abili ty to obta in governmenta l approval s of the merger on the proposed terms and schedule contempla ted by the parties; the fa ilure of stockholders of Hewitt Assoc iates, Inc. (“Hewitt ” ) to approve t he proposal to adopt the merger agreement; the fa ilure of the stockholders of Aon Corporati on (“Aon”) to approve t he proposal to approve t he issuance of shares of Aon common stock to Hewi tt stockholders in the merger; t he loss of key Aon or Hew itt employees follow ing the merger; t he ri sk that the Aon and Hewitt businesses will not be integrated successfull y; di sruption from the proposed transact ion making it more di ff icult t o ma inta in business and opera tional re lationships w ith customers, pa rt ne rs and ot he rs; the possibi lity that the proposed transact ion does not c lose, including, but not limited to, due t o the fa ilure to satisfy the c losing conditions; general economic conditions in di fferent countr ies in which Aon and Hewitt do business around the world; changes in globa l equity and fixed income marke ts that could affect the re turn on invested asse ts; fluc tuations in exchange and interest rates that could impac t revenue and expense; ra ting agency acti ons that could a ffec t Aon’s ability to borrow funds; changes i n t he funding status of Aon’s va ri ous de fi ned benef it pension pl ans and the impac t of any increased pension funding resulting from t hose changes; Aon’s ability to impl ement restruc turing initiat ives and ot he r i ni tiati ves intended to yie ld cost savings, and the abil ity to achieve those cost savings; the impact on r isk and insurance se rvices commission revenues of changes i n t he avail ability of , and the premium insurance carrie rs charge for, insurance and re insurance products, including the impact on premi um rates and marke t capac ity attr ibutable to cat astrophi c events; t he outcome of inquir ies from regula tors and investigat ions re lated to compliance w ith the U .S . Fore ign Corrupt Pract ices Ac t and non-U.S. anti-corruption laws; the impact of investi ga tions brought by U .S. state attorneys general, U .S. sta te insurance regula tors , U .S. federa l prosecutors, U .S. federa l regulators, and regul atory authorit ies in the U.K . and other countries; the impact of class act ions and indi vi dua l lawsuits including client class act ions, securities class act ions, de riva tive act ions and ERISA class act ions; the cost of resol ut ion of other contingent liabili ties and l oss contingenc ies, including pot entia l liabili ties a risi ng from e rror and omis sions c lai ms against Aon or Hewitt ; the ext ent to which Aon and Hewitt re tain existing cl ients and attrac t new businesses; t he extent t o which Aon and Hew itt manage certa in risks c reated i n connect ion w ith the var ious servi ces, i nc luding fiduci ary and advisory se rvices, among ot he rs, tha t Aon and Hew itt currentl y provide, or w ill provide in the fut ure, to clients; the impact of , and potenti al chall enges in complying with, legisla tion and regula tion in the jurisdic tions in which Aon and Hewitt ope ra te, pa rt icula rly given the global scope of Aon’s and Hewitt ’s businesses and t he possibi lity of confli cting regula tory requirements across jurisdic tions in which Aon and Hewitt do business; and the ability to rea lize the anti cipat ed benef its to Aon of the Benf ie ld merger. F urthe r information concerning Aon, Hewitt , and their business, including factors that potenti ally could mate ria lly af fect Aon’s and Hewitt ’s f inanc ial resul ts, is contained in Aon’s and Hewitt ’s f ilings with the Securit ies and Exchange Commi ssion (the “SEC” ). See Aon’s and Hewitt ’s Annual Report s on F orm 10-K and Annua l Report s to Stockholders for the fi sca l years ended December 31, 2009 and September 30, 2009, respec tively, and other public fili ngs w ith the SEC for a furthe r di scussion of these and other risks and uncertainti es applicable to our businesses. Ne ither Aon nor Hewitt undertakes, and each of them expressly di scla ims, any duty to update any forward- looking statement whether as a result of new information, future events or changes i n t he ir respecti ve expec tations, except as required by law. S afe Harbor S tatement

This communicati on does not constitute an offer to s ell or the sol icita tion of an offer to buy our securities or the solic itati on of any vote or approval. This communica tion is be ing made in respect of the proposed transact ion i nvolving Aon and Hew itt. In connect ion w ith the proposed merger, Aon filed wit h t he SEC a de fi ni tive joint proxy statement, which al so constitutes a prospec tus of Aon. The j oint proxy statement/prospect us was ma iled t o Aon stockholders and Hewitt stockholders on or about August 19, 2010. Be fore making any vot ing or investment decision, investors and stockholders are urged to read ca re fully in their entirety the de fi ni tive joint proxy statement/prospect us regarding the proposed transact ion and any ot he r rel evant documents f iled by eithe r Aon or Hew itt with the SEC when they become ava ilable because they cont ain and wil l contai n important information about the proposed transact ion. You may obta in copies of al l documents f iled w ith the SEC regarding this transact ion, f ree of charge, at the SEC ’s websi te (www.sec .gov), by accessing Aon’s websi te a t www.aon.com under the heading “Investor Rela tions” and then under the link “SEC Filings ” and from Aon by direc ting a request to Aon at Aon Corporation, 200 E. Randolph Stree t, Chicago, I llinois 60601, At tention: Investor Rel ations, and by accessing Hew itt ’s websi te a t www.hewit t.com under the heading “Investor Rel ations ” and then under the link “Report s & SEC Filings ” and from Hewitt by direc ting a request to Hewi tt at Hewitt Assoc iates, Inc., 100 Ha lf Day Road, Li ncolnshire, Illi nois 60069, Attention: Investor Rela tions. Aon and Hewitt and their respecti ve direct ors and executive officers and ce rta in other members of management and employees may be deemed t o be pa rt icipant s in the sol icita tion of proxies in res pect of the proposed transac tion. You can find information about Aon’s di rectors and executive officers in its de fi ni tive proxy statement f iled w ith the SEC on April 7, 2010. You can f ind information about Hewitt ’s di rectors and executive officers in its de fi ni tive proxy statement f iled w ith the SEC on December 16, 2009. Othe r information regarding the partic ipants in the proxy sol icita tion and a desc ripti on of their di rect and indirec t interests, by securit y holdings or ot he rwise , are conta ined in the de fi ni tive joint proxy statement/prospect us filed by Aon wit h t he SEC and wi ll be contained in ot he r re levant ma ter ia ls to be filed by Aon or Hew itt with the SEC when they become ava ilable . You can obta in free copies of these documents from Aon and Hewit t using t he contac t informati on above. Proxy

Agenda Sec tion 1 W hy is Aon Uniting w ith Hewitt ? Sec tion 2 Creating the Leading Human Capital Ente rpr ise in the World Sec tion 3 About Aon Consul ting Sec tion 4 About Hew itt Sec tion 5 About Aon Hewitt Sec tion 6 About the Deal Secti on 7 Time line and Conc luding Remarks

The merger be tween Aon Consul ting and Hewitt strengthens the core strat egy of Aon – the preeminent professional servi ces f irm focused on Ri sk and People Upon closing of the merger, Aon Corporation w ill be the c lea r global leader i n R isk (reta il and re insurance) and People The combined human capit al business segment w ill be cal led Aon Hew itt Combi ned Aon Hewitt revenue of $4.3 billion and 29,000 colleagues gl oba lly Cros s-sell opportunity is signi ficant through complementary product port folios across consulting, benef its administration and outsourcing Dive rsif ied presence across large corpora te and middle market Expec ted opera ting margin of 20% in Aon Hewitt ove r the long-term Strong cash f low generation w ith increased financia l flexibility and opportunity to invest in the business Smooth integration track record of bot h firms, no interruption to client service Global Leader in Risk and People Why is Aon Uniting w ith Hewitt ?

Agenda Sec tion 1 W hy is Aon Uniting w ith Hewitt ? Sec tion 2 Creating the Leading Human Capital Ente rpr ise in the World Sec tion 3 About Aon Consul ting Sec tion 4 About Hew itt Sec tion 5 About Aon Hewitt Sec tion 6 About the Deal Secti on 7 Time line and Conc luding Remarks

Substantia lly strengt hens the core strategy of Aon – to be the “Preeminent Professi ona l Services Firm” in the world focused on r isk and people Upon complet ion of the merger, Aon wi ll be the gl oba l leader in Risk and Human Capita l Solutions #1 ADVISOR ON RIS K GLOB ALLY #1 Pri mary Insurance Brokerage #1 Reinsurance Brokerage #1 Captive Management Leader in A ff inity Programs #1 IN HUMAN CAP ITAL SOLUTIONS #1 in B enef its Administrati on #1 in HR Benef its Process Outsourcing Leader in HR Consul ting Health & B enef its Retirement Investment Consul ting Compensation Human Capital Corporate Transactions Global Benef its Strengthens Leadership Position in Risk and People Marke t positions based on Business Insurance magaz ine 2009 Reader's Choice Awards. Othe r sources: Nelson Ha ll "HR Market Outsourcing Forecast 2009-2013“, November 2009.

Aon Consulting Strengths Hewi tt and Aon A re Strategi cal ly Aligned W ith Compl ementa ry Strengths Strengths Hewi tt Strong presence in the middle marke t Strong presence in the large marke t (>15000 employees) Additiona l capabilities in HR consulting and benef its broke rage (84% of consulting segment revenues) Strong capabil ities in outsourcing (66% of revenues) Led i ndustry in margi n expansion ove r the last 2 years (17% pre -tax margi ns i n 2008) Strong revenue growt h ove r the last 2 yea rs (7% organic grow th in 2008) Rela tionship with Ri sk S ervices and Reinsurance, both #1 insurance brokers worldwi de Truly world-class brand; amongst t op brands w ithin the HR Consulti ng industry Track record of investing in t he business through acquisit ions and talent Track record of investi ng in the business through acquisit ions and talent

Deliver ing Industry-Leading Client-Serving Capabil ities Strong brand in mi ddl e market benef its Approxima tel y $200 milli on outsourcing prac tice focused on middle marke t One of the la rgest, wholly-owned ne tworks of worldwide off ices with extensive specia lized global resources Gl oba l re tirement f irm providing broad-based actuaria l, pension risk and investment consulting US based pract ice focused on ta lent management Not servi ng HR BP O clients De liver ing a sec tor-based analyti cal approach of Radford and McLagan Brand Benef its Admin Health & Benef its Retirement Talent & Human Capital HR BP O Compensation Aon Consulting Global ly recognized as one of the foremost HR consul ting and out sourci ng providers Industry- leader i n gl oba l large corporate segment servi ng over 21 mi llion pa rt icipant s Industry- leadi ng stra tegies, data and anal yt ics and program management focused on la rge corporate segment Top-3 reti rement firm wit h broad based capabili ties across ac tuarial , pension risk, de fi ned contri buti on and investment consulting Gl oba l, full spectrum capabilities spanning leadership, ta lent and performance , HR e ffec tiveness and corporate transact ions World’s l argest HR BP O provider servi ng approxima tely 700,000 pa rt icipant s Compl ete range of compensat ion and rewards se rvices backed by powerful res earch and data Hewitt

Buyers of re tirement and healt h & benef its of ten t he same as risk produc ts Risk becoming increasi ngl y advice and consulting based Clients Distr ibution Simila r carrie rs i n many marke ts across the globe Sharing of brokerage infrastructure (e .g.; salesforce .com, web access pl atforms, cl ients servi ces) Market Access C ulture of professional servi ces Import ance of act ua ri al modeli ng and anal yt ics Use of common management tools and processes (e .g.; chief broking off ice rs, sale force.com, local marke t pl anning) Cult ure Produc t Success in the middle marke t dr iven by effect ive cross -sell Cl ients looking for global capabilities and infrastructure avail able across both busines s unit s P&C, HR and benef its r isks becoming more linked (e .g., absence management, worke rs comp, pandemic , people risk) Executives increasi ngl y vi ew ing pension pl ans as key r isk management issue Risk and Human Capita l Are Increasingly Linked

Leverage Hew itt ’s brand strength and product portfol io through Aon’s extensive mi ddl e market client base Increased premi um enhances re lationships w ith carr iers globa lly Shares ext ensive brokerage infrastructure such as salesforce .com Premium Hewi tt brand ava ilabl e to risk se rvices cl ient leaders C lients looking for global capabilities and infrastructure Risk and human capit al se rvices increasi ngl y becoming more linked Cross -sell Aon’s i ndustry-leadi ng r isk servi ces product portfol io through Hewitt ’s c lient base Leverage Aon’s brand strengt h and product port folio through Hewit t’s extensive large corporate client base Cross-sell Hewitt ’s benef its administration and HR B PO through Aon’s client base Creates Signifi cant C ross -Sell Opportunit ies Clients P roduct s Distr ibution Marke t Access

Agenda Sec tion 1 W hy is Aon Uniting w ith Hewitt ? Sec tion 2 Creating the Leading Human Capital Ente rpr ise in the World Sec tion 3 About Aon Consul ting Sec tion 4 About Hew itt Sec tion 5 About Aon Hewitt Sec tion 6 About the Deal Secti on 7 Time line and Conc luding Remarks

Business Overview Aon Corporation FY09 Tota l Revenue : $7.6B F Y09 Operat ing Income (O I) / Margin: $949M / 12.5% Aon Risk Solutions / Aon Benf ield Aon Consul ting F Y09 Revenue : $1.3B FY09 O I / Margin: $205M / 16% FY09 Revenue : $6.3B FY09 O I / Margin: $914M / 15% Health & Benef its Retirement Compensation Human Capital Corporate Transactions Global Benef its Risk Solutions Property Ris k Management Casual ty Risk Management Captive Management Environmental Reinsurance Facultati ve Reinsurance Trea ty Reinsurance Investment Banking Group

Aon Consulting Capabil ities and Services Aon Consul ting i s shaping the workpl ace of the future through benef its, ta lent management, and rewards strategies and solutions. We leverage our gl oba l network of of f ices, unmatched t alent , innova tion, thought leadership, and opera tional exce llence to de liver distinc tive va lue to our clients. We a re a gl oba l leader in healt h and benef its consulting, di fferentia ted by size and sca le as we ll as the way we he lp our clients. Health and Benef its W e help dr ive organizationa l success through the leadership of talent and mi tigati on of human capit al risk. Human Capita l Consul ting W e serve 1.2 mi llion pa rt icipant s in large and mid-sized organizations, spanning a ll geographi es and industr ies. Employee Benef its Outsourcing We counsel companies undergoing corporate transact ions address leadership struc ture , organizationa l ef fectiveness, and program efficacy and impac t. Corporate Transactions We provide comprehensive and integrated re tirement servi ces for programs sponsored by domestic and mult inationa l organizations. Retirement We have one of the largest, whol ly-owned net works to provide support and advice to clients in more than 100 countries. Gl oba l Benef its Our experts in McLagan and Radford help clients using marke t compensat ion and executive reward stra tegies. Globa l Compensation

Exceptional ly Strong Business Prof ile , G lobal Footprint, and Marke t Positi on Achi eved global ne t revenue of $1.3 billion in fiscal 2009 Industry leading pre-tax margins of 17% Cli ents include ha lf of the FORTUNE 500® Selected by the readers of Business Insurance as the “Best Employee Benef it Consul ting F irm” in 2006, 2007, 2008, and 2009 Leaders have been recognized by Consulting Magaz ine as Top 25 Consultants in 2008 and 2010 - Bal Dail and Ka thryn Hayley, respecti ve ly 6,300 coll eagues; 229 offices in 90 countries Serve ove r 10,000 clients worldwide

Mi ssion and Va lues 2005 4t h/ 5t h ranked human capit al and management consulting firm $1.2b revenue; $110m PTI Strong, dedica ted team “Best kept secret ” Aon Consul ting Mi ssion: Shaping the workpl ace of the future through benef its, ta lent management, and rewards stra tegies and sol ut ions Aon Leadership Mode l De liver di stinct c lient va lue Deve lop unmatched t eams Build di fferentia ted capabilities through innova tion De liver busi ness resul ts wit h exce llence Live our values

Aon Consul ting’s Global Presence 90 countr ies 229 off ices 6,300 associa tes / colleagues Serving ha lf the Fortune 500 and ove r 10,000 clients worldwide Aon Consul ting

Balji t Da il – Co-CEO, Aon Consul ting and COO, Aon Benf ield Ba ljit “Bal ” Da il is CEO of Aon Consul ting’s internationa l businesses and gl oba l practices. He is also Chie f Operat ing O fficer for Aon Benf iel d. Consul ting Magaz ine named Da il one of it s Top 25 Consul tants in 2010. Dail was key in making sure t he billion doll ar-pl us acquisit ion w ith Benf ield G roup was successful. Since joining Aon in 2005, Dail has also se rved as COO, Aon Consul ting; CIO , Aon Corporati on; Head of G lobal Offshoring, Aon Corporation; and Co-leader of the Simplif ica tion Initia tive, Aon Corporation. Pri or to joining Aon, Da il worked at McK insey and Company, where he was a partne r worki ng across a wide va ri ety of industr ies, including finance , re tail, insurance, telecom and techonology. Pri or to McKi nsey, Da il was Vice President of Strategi c Planning, at Starwood Hotels and Resorts, and be fore tha t served in l eadership roles at JP Morgan, Marks & S pencer and Ford Motor Company. Da il recei ved his Bache lor of Science Honours degree in Compute r Science from the University of Warwi ck, U.K .

Kathryn Hayley – Co-CEO, Aon Consul ting Ka thryn Hayley is co -Chief Executive O fficer of Aon Consul ting, w ith responsibil ities for the Americas. Since Hayley joined Aon Consul ting i n June of 2006, she has buil t a world c lass leadership team that is provi di ng innova tive sol ut ions for employers in healt h care, re tirement, ta lent management and outsourcing. Previously, Hayl ey spent 21 years at Del oi tte Consul ting s ervi ng in numerous leadership posit ions . S he was Mi dwest regiona l managing direct or at Deloitt e, responsible for a prac tice specia liz ing i n human capit al, stra tegy and opera tions, technology integration and enterpri se applica tions. In pa rt icula r, Hayley was involved in the deve lopment and impl ement ation of some of the firm ’s largest and most complex technology impl ement ation projec ts in Financ ial S ervices and other industr ies. Hayl ey recei ved her M.B .A . in Finance and Marke ting from Northwestern University, and he r B ache lor of Science degree in Applied C ompute r Science from Illi nois S tate University.

Agenda Sec tion 1 W hy is Aon Uniting w ith Hewitt ? Sec tion 2 Creating the Leading Human Capital Ente rpr ise in the World Sec tion 3 About Aon Consul ting Sec tion 4 About Hew itt Sec tion 5 About Aon Hewitt Sec tion 6 About the Deal Secti on 7 Time line and Conc luding Remarks

Note – Ne t revenue, opera ting income and margin amounts are presented on an underlying basi s (adj ust ed for unusua l items). Business Overvi ew Hewitt Assoc iates FY09 Net Revenues: $3.0B FY09 Operating Income (O I)/ Margin: $425MM / 14.1% Benef its Outsourcing FY09 Ne t Revenues: $1,550MM FY09 OI / Margin: $387MM) / 25% HR Business Process Outsourcing (HR BPO) FY09 Ne t Revenues: $480MM FY09 OI / Margin: $(15)MM / (3)% Consul ting F Y09 Ne t Revenues: $1,012MM FY09 OI / Margin: $144MM / 14% • De fined B enef it (DB) • De fined Cont ribution (DC) • Health and W elfare (H&W) • Additiona l standalone complementary point soluti ons — Absence management — Spending account administration — Dependent audit • Core process management — Workforce administration, payroll, customer servi ce • Ta lent — Performance, succession, recrui ting, lea rning • Reward — compensat ion admin. • Measure and manage — Workforce analyti cs, supplier management • Retirement & Financ ial Management (RF M) • Ta lent and Organiza tion Consul ting (TOC ) • Health Management (HM) • Communicati ons (COMM)

Hewitt Assoc iates Is a Global HR Consul ting and Outsourcing Company Since 1940, we have he lped our clients and their people succeed toge ther by antic ipating and sol vi ng the ir most complex benef its, ta lent, and financia l chall enges. Whethe r your organization is a complex global organization, a growi ng mi ds ized business, or somewhere in be tween, we can he lp ensure that the investments you make in people succeed. Benef its Tal ent Financ ial W e he lp control the risk assoc iat ed with bene fi t programs and their pot entia l impact on business pe rformance and financ ial resul ts. We he lp manage the potentia l of cr itica l ta lent, executives, and next -generation leaders while mi ni mizing the re tention and compliance r isk of a globa l workforce. W e he lp balance t he potential and risks of benef it program investments and increase the speed and return on the ir most complex M&A transact ions.

We Are The HR Industry Leader Achi eved global ne t revenue of $3.0 billion in fiscal 2009 Clients i nc lude more than one-ha lf of the FOR TUNE 500® More than 95% of our largest c lients have worked with Hew itt for at least f ive years Recognized by FOR TUNE as one of America ’s Most Admired Companies Ranked by Business Insurance as the world’s t hird-largest empl oyee benef its consulting firm in 2009 Ranked #22 on Gl oba l Outsourcing 100 by the Inte rnat ional Assoc iation of Outsourcing Professi ona ls Named Consul ting F irm of the Year by China Sta ff f rom 2001–2009 Named Inte rnat ional Benef its Consul tant of t he Year by G lobal Pensions Named 2010 UK Ac tuarial and Investment Consul tancy of the Year by Professi ona l Pensions 23,000 associa tes i n more than 30 countries

Our Mi ssion and Va lues Hewitt ’s Mi ssion: Making the world a bett er pl ace to work The va lues we adhere to a re simple, re flecting on what is mos t important from our 70 years in business. Trea t people w ith respect and di gnit y Achi eve exce llence Work toget he r Conduc t ourselves wi th integr ity

Hewitt Globa l Offices • Argentina • Australia • Austr ia Be lgium Brazil • Canada • Channel Islands • Chile China • Cyprus • Czech Republic • France Germany Greece Hungary India • Ireland • Israe l* Ita ly • Japan • Korea • Ma laysia • Maurit ius • Mexico Morocco* Ne therlands New Zea land • Philippines • Puerto Rico • Poland — Romania* Russia* Singapore Slovakia * • Slovenia * S outh Africa* • Spain • Sweden • Swi tze rland • Tha iland • Turkey* • Ukraine* • United Arab Emirat es Uni ted Kingdom • United Stat es of America * Partner or Alli ance Offi ce

Russell F radin – Chairman of t he Board of Di rectors and CEO Russ Fradin joined Hewitt in September 2006, br inging a unique bl end of outsourcing, opera tions, and stra tegic consulting experience. He immediat ely focused the company on a set of four strategi c pr ior ities —keeping cl ients first, crea ting a rewarding work experience, growi ng w ith intention, and ge tting lean. Efforts to enhance hi gh-qua lity servi ce de livery have resulted in improved c lient satisfac tion scores worldwide . Initia tives t o improve associa tes ’ work experience have yi elded signif icant ga ins in engagement and reduc tions in turnover. The company’s ongoing focus on streamlining the cost structure has led to signif icant margi n improvements in all three of its businesses. Hew itt has fue led grow th by enter ing new marke ts, expanding gl oba lly, and adding complementary servi ces. P rior to joining Hew itt , Russ served as presi dent and CEO of The BIS YS Group, a financ ial servi ces administration firm. Under his leadership, the business re turned to a 6 percent growt h rat e and margi ns i mproved by 10 percent ove r a two-year per iod through a combination of of f-shoring, technology upgrades , and ot he r cost reduc tions. Russ ga ined his opera tions experience over seven years w ith outsourcing giant ADP. As presi dent of its G lobal Employer Services group, he oversaw 28,000 employees and more t han 400,000 clients gl oba lly. Russ orchestra ted a growt h program that inc reased revenues 66 pe rcent, f rom $2.7 bi llion to $4.5 bi llion, and improved the group’s profi t margi n by more than 500 basis points. Additiona lly, he succeeded in di ve rsi fying the group, increasi ng non-payroll revenue from 11 pe rcent to 35 pe rcent, and improving client satisfac tion by more than 20 pe rcent in every business. Russ developed his stra tegic busi ness acumen during 18 years at McKinsey & C ompany, including multi-year assignment s at two of McKi nsey’s largest c lients. Russ founded and grew the New Jersey off ice into one of the f irm’s most profi table . Russ serves on the Board of Di rectors for both Gartner and The Executives ’ Club of Chicago. He also serves on the Board of Ambassadors for CEOs Against Cancer—American Cancer Socie ty. In addition, he is a member of G100, The I lli nois Business Roundtable, the Civic Commit tee of The Commercia l Club of Chicago, and pa rt icipa tes on the WSJ CEO Counc il. He holds a maste r ’s degree in business administration from Harvard Business School and a bachelor of science degree in economics with a concent ra tion in finance from the Wharton School of the University of Pennsyl vania. “Russ has done a tremendous job enhanci ng the momentum of Hewitt ” “He has a strong background in opera tions from hi s time a t ADP” “I know tha t Russ is exci ted to join our team and wi ll be reaching out to Aon Consulting leaders t o l earn about our organization and to s eek your counsel” – Andrew Appel (COO, Aon)

Agenda Sec tion 1 W hy is Aon Uniting w ith Hewitt ? Sec tion 2 Creating the Leading Human Capital Ente rpr ise in the World Sec tion 3 About Aon Consul ting Sec tion 4 About Hew itt Sec tion 5 About Aon Hewitt Sec tion 6 About the Deal Secti on 7 Time line and Conc luding Remarks

Leading global brand in human capit al solutions and advice Dive rsif ied and complementary client portfolio covering both large corpora te and mid-marke t clients Expanded ability to provi de additional products and servi ces t o meet the ful l spect rum of r isk and human capit al needs Impressive globa l footpri nt which we will use to fue l growt h The strongest t eam of professionals i n the human capital industry – able to provide the full spectrum of support for our clients for their most complex human capit al chall enges Financ ial resources to fund innova tion and future grow th Simila r goal s and va lues rela ting to client focus, people, innova tion, exce llence, teamwork and integr ity that w ill he lp wi th the integration of our businesses Everything we need to be one of the best known business brands i n the world Aon Hewitt

Balanced P ortfolio of Complementary Service Offe r ings Extensive middle marke t cli ent base Leader in bene fits brokerage Recognized as a strong provide r of HR consul ting and outsourcing servi ces Aon Consul ting S trong presence in the large market Strong capabil ities in outsourcing World -class brand; amongst top brands w ithin the HR Consulti ng industry Hew itt Combi na tion creat es industry-leadi ng produc t portfol io High mix of recurri ng revenues Business lines focused on growt h segments of the marke t Aon Hewitt FY09 Consul ting Revenue $1.3 bi llion FY09 Tota l Revenue $3.0 bi llion FY09 Consul ting Revenue $4.3 bi llion Bene fits Admin $191 15% Consul ting $1,075 85% Consulting $1,012 33% Benef its Admin $1,550 51% Out -sourcing $480 16% Consul ting $2,087 49% Bene fits Admin $1,741 40% Out -sourcing $480 11%

30+ countri es 107 offices 23,000 associa tes / colleagues Global Geographic Footprint Hewitt 120 countries 500 off ices 36,000 associa tes / colleagues Aon Corporation

Agenda Sec tion 1 W hy is Aon Uniting w ith Hewitt ? Sec tion 2 Creating the Leading Human Capital Ente rpr ise in the World Sec tion 3 About Aon Consul ting Sec tion 4 About Hew itt Sec tion 5 About Aon Hewitt Sec tion 6 About the Deal Secti on 7 Time line and Conc luding Remarks

Hewitt will merge wi th Aon for $50 per share, consisting, on a fully diluted basis, of 50% cash and 50% Aon stock, based on the closing pr ice of Aon stock on Jul y 9, 2010 Consi deration re flects a mult iple of 7.5x Hewitt ’s F Y2010 consensus estima tes EBITDA Crea tes gl oba l leader in human capit al sol ut ions w ith combined Aon Hewitt revenues of $4.3 bil lion Expec t to deli ve r $355 milli on of annual savi ngs in 2013 Transac tion is expec ted to be acc re tive on a GAAP EP S basis in 2012, on an Adjusted EP S basis in 2011 and signi ficantly acc re tive t o cash earnings in 2011 Genera tes st rong cash f low w ith increased financ ial flexibility Expect to c reat e $1.5 bi llion of sha reholder value Highlights of the Transaction

Pri mary dr ivers of expected opera ting margin improvement include: $355 mi llion of synergies, decreasing intangible amort iza tion expense and opera tional improvement in HR BP O Expec t to achieve long-term opera ting margi n in Aon Hewitt of 20% 20% Long -Term Operat ing Margin in Aon Hewitt of 20% Aon Consulting Hewitt Aon Hewitt

Aon and Hew itt generated $2.2 bi llion of tota l EBITDA in FY2009 Aon and Hewitt combined will provide grea ter cash flow flexibility to creat e long-term shareholder value High mix of recurr ing revenue and complementary product port folio provides grea ter cash f low st ability Strong Cash Flow Genera tion (EBITDA) Aon Hewitt Aon Hewitt

Agenda Sec tion 1 W hy is Aon Uniting w ith Hewitt ? Sec tion 2 Creating the Leading Human Capital Ente rpr ise in the World Sec tion 3 About Aon Consul ting Sec tion 4 About Hew itt Sec tion 5 About Aon Hewitt Sec tion 6 About the Deal Secti on 7 Time line and Conc luding Remarks

Quest ions Genera l questions about deal, what it means, and wha t can be said about it Client communica tions questions Questions about impac t of dea l on regions or prac tices Type of Quest ion Resource/ Cont act Visit the Aon Hewitt Integra tion Porta l via Know ledge Exchange (KE) or The S ource for Key Messages and Quest ions and Answers (Q&A) Visit the Aon Hewitt Integra tion Porta l via Know ledge Exchange (KE) or The S ource for Key Messages and Quest ions and Answers (Q&A) Region/Prac tice leaders

Appendix

Transaction Terms: Hew itt will merge wi th Aon for $50 pe r sha re , consisting, on a fully diluted basis, of 50% cash and 50% Aon stock, based on the closing pr ice of Aon stock on Jul y 9, 2010 Aggrega te fully diluted equity value of the transac tion is $4.9 billion consisting of $2.45 billion of cash and t he issuance of 64.0 mi llion shares Consi deration re flects a mult iple of 7.5x Hewitt ’s F Y2010 consensus estima tes EBITDA Timing / Ma jor Mi lestones: We expec t to close the transac tion by mi d-November Ma jor completi on mi lestones: - Prepare and f ile joint proxy statement / prospec tus - Receive regula tory approval s - Receive stockholder approval s Transaction Terms and Timing / Ma jor Mi lestones

$1.5 billion of va lue c reation represents the combined Discount ed Cash Flow (DCF) value of Hewitt pl us synergies, less the purchase pr ice Transaction creat es signi ficant va lue through ne t run -ra te synergies of $355 milli on Transaction ut ilizes additional leverage agai ns t under-leveraged Hewitt cash flow generati on while ma inta ining current investment grade credit ra tings Expec t to C reate $1.5 bi llion of Shareholder Va lue $4.9B $1.5B $6.4B

Transaction w ill be financed w ith 50% cash and 50% stock in order to mainta in current investment grade credit ratings of BBB+/ Baa2 Credit benef its of the transacti on include: Increased revenue base Increased di ve rsi ty of revenue base Increased EBITDA and EBITDA margi ns ove r the long -term Financ ing commitments for 100% of cash considerati on a re in place via a $1.5 billion br idge fac ility and a $1.0 bi llion bank term loan Al l of the financ ing is expec ted to be completed in the U.S. inc luding: A $1.0 bi llion three -year bank term loan matur ing 10% in year 1, 10% in year 2 and 80% in year 3, with pr ic ing a t L ibor + 250 bps A $1.5 bi llion bridge facilit y The company expec ts to i ssue unsecured notes pr ior to draw ing on the br idge facilit y Expec t to Ma intai n Investment Grade C redi t Ratings