Credit Suisse First Boston Annual Healthcare Conference November 17, 2005

2 Statements included in this presentation or in the oral comments made as part of this presentation may contain forward-looking statements, including but not limited to statements of the Company’s plans, objectives, expectations or intentions, that involve risk and uncertainties. The Company’s actual results may differ significantly from those projected or suggested in any forward-looking statement due to a variety of factors, which are discussed in detail in the Company’s filings with the Securities and Exchange Commission. Forward-Looking Statements

3 Today’s Challenging Environment: Keeping the Prescription Drug Benefit Off the Endangered List

Unmanaged Prescription Drug Trend Plan sponsors will likely increase the use of PBM tools to manage drug spend Source: 2004 Drug Trend Report

5 Our Value Proposition: Complete Alignment To reduce pharmacy costs, without compromise to health outcomes, while maximizing patient satisfaction

6 More Number of Drugs Fewer Benefit Options Impact on ClientImpact on PatientImpact on ESI Lower drug cost More choice Lower co payment More choice Higher Profit/Rx More Flexibility Alignment –Formulary Management Therapy Class We Provide Flexible Formulary Management 1. Select number of drugs in therapy class 2. Determine formulary control 3. Drive towards lowest overall cost # of drugs # of drugs # of drugs Open Differential Co-pay Closed Lowest Overall Cost

7 Alignment - Retail Network Management States Available Pharmacies Most Inclusive Network Most Restrictive Network TRICARE Access Minimum CA 5,6445,0713, NY 4,4444,2241, TX 4,2363,8211, FL 4,0203,6701, PA 2,9702,8251, Greater Management Higher Profit/Rx More Flexibility Lower co payment More choice Lower drug cost More choice Impact on ESIImpact on PatientImpact on Client Higher Profit/RxLower co paymentLower drug cost Impact on ESIImpact on PatientImpact on Client

8 Impact on PatientImpact on ESI Lower drug costLower co paymentHigher Profit/Rx Alignment – Clinical Programs Clients using step therapy realize on average a 2 percentage point increase in generic utilization Plan Designs Encourage Greater Use of Generics and Preferred Low-cost Brands

9 Alignment – Home Delivery Impact on ClientImpact on PatientImpact on ESI Lower drug cost Choice Lower co payment Choice Higher profit/Rx We Offer Highly Efficient, Cost-effective Home Delivery

10 * Represents network claims plus 3 times home delivery claims –home delivery claims are 90 days vs. 30 days in the network. Excludes UHC claims Increased home delivery penetration Home Delivery Helps Manage the Cost of Maintenance Drugs Alignment – Growing Demand for Home Delivery

11 Alignment – Generic Utilization Impact on ClientImpact on PatientImpact on ESI Lowest drug costLowest co paymentHighest profit/Rx Source: From public filings Express Scripts Leads in Generic Utilization

12 ESI Analysis Represents over 20% of 2004 branded drug sales Our Clients and Members Will Benefit From a Growing Generic Opportunity Alignment – Growing Generic Opportunity

Alingnment – Specialty Pharmacy Sources: IMS Data through November 2004 Wall Street Equity Research, 2004 CMS National Healthcare Expenditure Projection: 2003 – 2013 Data on file: CuraScript Total Outpatient Pharmacy Spend $190 Billion 2008 Projected Outpatient Pharmacy Spend $283 Billion 26% 18% Traditional Spend $210 Billion Specialty Spend $73 Billion Specialty Spend $35 Billion Traditional Spend $155 Billion Impact on Client Impact on Patient Impact on ESI Lower drug cost Lower co payment Higher profit/Rx Improved reporting Improved quality of care Higher client satisfaction Clients are Seeking Solutions for High-cost Specialty Drugs

Express Scripts’ specialty penetration has increased from 2% to 30% in the first 5.5 quarters of our CuraScript acquisition. Percentage of Plan Costs Source: Express Scripts Analysis. CuraScript Penetration into Express Scripts

Priority Acquisition - Strategic Rationale  Creates one of the largest specialty franchises in the U.S. –$3+ billion annual specialty revenues –One of the fastest growing sectors in healthcare –Sector remains fragmented and market structure continues to emerge (greenfield opportunities)  Fills key therapy classes within CuraScript portfolio – “one-stop shopping for clients” –Infertility (number one fertility franchise) –Pulmonary Fibrosis –Pulmonary Hypertension –Home Infusion  Offers additional capabilities –Specialty distribution capabilities –Supply chain services  Leverages PBM core competencies (payor and manufacturer relationships, mail order pharmacies, clinical and trend management expertise) –Synergy potential –Increased value proposition for clients (single vendor, integrated reporting)

16 What Are the Savings? Availability of Proven PBM Cost Management Tools Will Produce 20%–25% Savings (CBO) Paid by Cash Customer at Pharmacy Retail, Clinical. Formulary And Rebate Savings 24% Home Delivery Savings 6% Paid by Express Scripts Clients Total Savings 30% COSTCOST Retail Pharmacy Cash Price Express Scripts Client Savings Express Scripts Client Costs

17 Alignment – A Win-Win-Win Proposition Retail Non-pref. Brand Retail Pref. Brand Generics Mail Pharmacy Increased Savings Opportunities: Client Member Increased Profit Opportunities: Express Scripts Moving to preferred brands, home delivery and generics We make money by saving clients and members money Moving to preferred brands, home delivery and generics

18 We Deliver Against Client and Patient Expectations: To make the use of prescription drugs safer and more affordable

19 Client/Patient Focus By membership Health Plan Sponsors Recognize Express Scripts Single Focus on Making Prescription Drugs More Affordable Why Express Scripts? Alignment With Clients Generics Specialty

Upsell Pipeline is Strong Significant potential to continue to manage client trends in key product categories New products continue to be developed and rolled out Strong track record of success 10,000 ( '000 Lives) 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 Home Delivery Generic Enforcement Narrowing Formularies New Clinical Products Specialty/CuraScript Three Tier Sold Weighted Pipeline

21 Client Satisfaction Steadily Improving Service and satisfaction metrics have increased consistently quarter over quarter since 2003 with an early spike in 2005 Exceed 60% 65% 70% 75% 80% 85% 90% 95% 100% ESI Performance Expectations Likelihood to Recommend Likelihood to Renew q05

22 Our Financial Results Express Scripts has demonstrated a proven track record

23 Q Highlights – Adjusted EPS of $0.67*, up 34% from $0.50* last year – Cash flow from operations of $214.6 M vs. $150.0 M last year Repurchased 4.0 million shares for $219.9 million – Generic drugs were 55% of total prescriptions vs. 51% last year – Gross profit of $293.2 M, up 25% Gross profit per adjusted claim was $2.13, up 20% EBITDA per adjusted claim was $1.32, up 19% – Raised EPS guidance for 2005 *Excludes prior period tax benefit of $0.01 in Q and non recurring charge of $0.10 for legal defense costs in Q – reconciliation of reported EPS to adjusted EPS is included in Table 4 of the 3Q 2005 earnings release

24 Quality of Earnings (1)Reflects a $70-$75 million reduction in Q due to one-time impact of implementing a new wholesale purchase agreement (2)Excludes a $0.04 per share charge for the early retirement of debt (3)Excludes a $0.10 charge to increase legal reserves for the cost of defense. (4)Excludes an $0.08 and $0.01 prior year tax benefit in Q2 and Q3, respectively (1) (2) * Reflects a 12-month moving average of free cash flow (cash from operations less CapX) (3) (4) (4)

25 Components of EPS Growth — 2004 * Excluding $25 million charge to increase legal reserves for the cost of defense and $5.5 million termination payment received 6% 7% 8% 2004

Major PBM Prescription Growth Note: Rx growth for Medco, Caremark reflect as configured today * YTD

27 Claims Volume Vs. EPS Growth (1)Excludes a $0.10 charge to increase legal reserves (4) Reflects the June 1 st anniversary of the DoD retail contract (2)Excludes an $0.08 prior year tax benefit (3)Excludes a $0.01 prior year tax benefit (2) (3) (1) Expanding Margins Supports Strong EPS Growth on More Modest Claims Growth (4)

Profits Per Claim Growth EBITDA* per adjusted claim * A reconciliation of EBITDA to net income and to net cash provided by operating activities can be found in the Investor Relations section of Express Scripts’ Web site, under Presentations. ** Excluding $25 million charge to increase legal reserves for the cost of defense and $5.5 million termination payment received. Pricing can be lowered as clients tighten formulary compliance, increase home delivery, utilize generics and restrict retail networks. These changes result in lower prices to our clients and greater profits to Express Scripts. 11% CAGR

Gross Profit* / SG&A* / EBITDA per Adj. Rx Future EBITDA per Adj. Rx Must Come From Gross Profit per Adj. Rx * Before depreciation and amortization ** Excluding $25 million charge to increase legal reserves for the cost of defense and $5.5 million termination payment received. Source: Express Scripts Analysis.

30 Focus on Return on Invested Capital (ROIC) ROIC is our Preferred Performance Metric * Reflects operating income less tax divided by average invested capital, which consists of stockholder’s equity, plus interest bearing liabilities plus long-term deferred income taxes, net. ** Excludes $25 million charge to increase legal reserves for the cost of defense and 5.5 million termination payment received

31 W hy Express Scripts? Industry-Leading ROIC We Lead Our Peer Group in ROIC Performance Source: Express Scripts Analysis

32 Peer Group Total Return YTD ESI’s 104% YTD return is more than 3 times our peer group Peer group avg. 28.8%

33 S&P Total Return – YTD Only 1 company in the S&P 500 exceeded ESI’s total return to stockholders of 104.2% YTD thru Note: Returns reflect stock price increase plus dividend yield

34 Our Value Proposition Will Continue to Drive Growth Making the use of drugs safer and more affordable is more important than ever Plan sponsors will increasingly deploy our tools Express Scripts is well-positioned for sustainable growth Strong market fundamentals/new business opportunities Increased use of home delivery and generic drugs Growth in management of specialty pharmacy Productivity and capital structure improvements We have taken a different approach Alignment -- we make money by saving our clients money Strategic acquisitions have enhanced our value proposition