William Blair 25th Annual Growth Stock Conference

June 16, 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

Our Interests are Aligned with Clients and Patients:

To make the use of prescription drugs safer and

more affordable

4

More Number of Drugs Fewer

Alignment –Formulary Management

Therapy Class

We Provide Flexible Management of

the Supply Chain 1. Select number of drugs in therapy class

# ofdrugs

# ofdrugs

# ofdrugs

# ofdrugs

5

More Number of Drugs Fewer

Alignment –Formulary Management

Therapy Class

We Provide Flexible Management of

the Supply Chain 1. Select number of drugs in therapy class 2. Determine formulary control

Ben

efi

t O

pti

on

s # ofdrugs

# ofdrugs

# ofdrugs

# ofdrugs

Open

DifferentialCo-pay

Closed

6

More Number of Drugs Fewer

Ben

efi

t O

pti

on

s

Impact on Client

Impact on Patient

Impact 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 Management of

the Supply Chain 1. Select number of drugs in therapy class 2. Determine formulary control 3. Drive towards lowest overall cost

# ofdrugs

# ofdrugs

# ofdrugs

# ofdrugs

Open

DifferentialCo-pay

ClosedLowestOverall

Cost

7

Alignment - Retail Network Management

States

Available Pharmaci

es

Most Inclusive Network

Most Restrictiv

e Network

TRICARE Access

Minimum

CA 5,644 5,071 3,881 283NY 4,444 4,224 1,829 300TX 4,236 3,821 1,827 579FL 4,020 3,670 1,966 469PA 2,970 2,825 1,687 432

Greater Management

•Higher Profit/Rx•More Flexibility

•Lower co payment•More choice

•Lower drug cost•More choice

•Impact on ESI•Impact on Patient•Impact on Client

Higher Profit/RxLower co paymentLower drug cost

Impact on ESIImpact on PatientImpact on Client

8

Impact on Client

Impact on Patient

Impact on ESI

Lower drug cost

Lower co payment

Higher Profit/Rx

Alignment – Clinical Programs

4.5

13.0

0

2

4

6

8

10

12

14

Mil

lio

ns

Q1 2003 Q4 2004

Members in Step Therapy 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 Client

Impact on Patient

Impact on ESI

Lower drug cost

Choice

Lower co paymentChoice

Higher profit/Rx

We Offer Highly Efficient, Cost-effective

Home Delivery

10

16.4%

18.5%

22.6%

20.2%

17.2%

13.8%

15.8%

13.1%0

100

200

300

400

500

600

1996 1997 1998 1999 2000 2001 2002 2003 2004

Ad

just

ed C

laim

s* (

mill

ion

s)

13.0%14.0%15.0%16.0%17.0%18.0%19.0%20.0%21.0%22.0%23.0%24.0%

% m

ail p

enet

ratio

n

Total Adjusted Claims Mail Penetration

* Represents network claims plus 3 times home delivery claims –home delivery claims are 90 days vs. 30 days in the network.

Excludes UHC claims

D IVERSIFIED®

Increased home delivery penetration

Home Delivery Helps Manage the Cost of Maintenance Drugs

Alignment – Growing Demand for Mail

11

Alignment – Generic Utilization

Generic Utilization Rate

38%40%42%44%46%48%50%52%54%

Q102

Q202

Q302

Q402

Q103

Q203

Q303

Q403

Q104

Q204

Q304

Q404

Q105

ESI PBM B PBM C

Impact on Client

Impact on Patient

Impact on ESI

Lowest drug cost

Lowest co payment

Highest profit/Rx

Source: From public filings

Express Scripts Leads in Generic Utilization

12

$10.3

$11.3

$10.4 $10.4

$9.8

$9

$10

$10

$11

$11

$12

$ -

bil

lio

ns

2005 2006 2007 2008 2009

U.S. Sales for Brand Products with Patent Expirations From 2005-2009

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

13

100%$35 Total

19%3.5Other

1%0.5Growth Hormone

1%0.5Infertility

2%0.6RSV prophylaxis

4%1.5Rheumatoid arthritis

4%1.5Multiple sclerosis

4%1.5Transplant

5%1.6Hepatitis C

5%1.6Hemophilia

9%3.2Renal

10%3.4HIV/AIDS

36% $12.6Oncology

Biotech Market, $35B, 18%

Traditional Rx Market,

$155B, 82%

Alignment – Specialty Pharmacy

Specialty Market

2004

Billions

Source: ESI Analysis

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

14

CuraScript Penetration intoExpress Scripts

Retail

CuraScript

Mail

82% 73%

70% 69% 66%

2%13%

17% 20%25%

16%14%

13% 11%

9%

100

90

80

70

60

50

40

30

20

10

0Q1 2004Q2 2004Q3 2004 Q4 2004 Q1 2005

CuraScript Continues to Capture an Increased Share of Our Client’s Specialty Spend

Perc

en

tag

e o

f P

lan

Costs

15

What Are the Savings?

Availability of Proven PBM Cost Management Tools Will Produce 20%–25% Savings (CBO)

Paid byCash Customer

at Pharmacy

Retail, Clinical.Formulary

And RebateSavings 24% Mail Savings

6%

Paid byExpress ScriptsClients

Total Savings 30%

COST

Retail Pharmacy Cash Price

Express Scripts Client Savings

Express Scripts Client Costs

16

Alignment – A Win-Win-Win Proposition

Retail Non-pref. Brand

Retail Pref.

BrandGenerics

Mail Pharma

cy

Increased Savings

Opportunities:

Client

Member

Increased

Profit

Opportunities:

Express Scripts

Moving to preferred brands, mail and generics

We make money by saving clients and members money

Moving to preferred brands, mail and generics

Moving to preferred brands, mail and generics

17

PBM’s Are Part of the Solution for Medicare

$1,610

$2,322

$3,160

$0

$500

$1,000

$1,500

$2,000

$2,500

$3,000

$3,500

2000 2003 2006E

Average Annual Drug Spend

Among Medicare Population

Source: Actuarial Research Corporation

The Medicare Prescription Drug Act will shape

the direction of our industry for years to come

• ESI is well positioned for 2006

• Our 2006 offensive strategy is to help our managed care and carrier clients profitably grow their MA-PDs and PDPs

• We are building the foundation for 2007

18

Benefits of ePrescribing

Prescription & Pharmacy Benefit Information

Point of Sale

Point of Care

Benefit / Gain

ClinicalMessages at pharmacy

Physicians see clinical issues

Better informed, safer prescribing

Formulary

Enforcement after prescribing

Awareness at prescribing

Better choices, increased generics

BenefitReferenced at pharmacy

Real-time guidance

Cost-effectiveness, fewer callbacks

Medication History

Partially known

History while prescribing Patient safety

Prescription

Carried, faxed, called, mailed

Convenience at pharmacy

More efficient, patient safety

Medicare Part D Will Advance Important Initiatives Including e- Prescribing

19

We Deliver Against Client and Patient Expectations:

To make the use of prescription drugs safer and

more affordable

20

Client/Patient Focus

Commercial26%

Canada10%

Managed Care39%

Public Sector25%

By membership

Health Plan Sponsors Recognize Express Scripts Single

Focus on Making Prescription Drugs More Affordable

Why Express Scripts?• Alignment With

Clients• Generics• Specialty

21

2006 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

Liv

es)

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

Hom

e Del

iver

y

Gener

ic E

nfor

cem

ent

Nar

rowin

g Fo

rmul

arie

s

New

Clin

ical

Pro

duct

s

Spec

ialty

/Cur

aScr

ipt

Thre

e Ti

er

Sold Weighted Pipeline

22

Client Satisfaction Steadily Improving

• Service and satisfaction metrics have increased consistently quarter over quarter since 2003 with an early spike in 2005

Exceed60%

65%

70%

75%

80%

85%

90%

95%

100%

ESI PerformanceExpectations

Likelihood toRecommend

Likelihood toRenew

2003

2004

1q05

23

Our Financial Results

Express Scripts has demonstrated a proven track

record

24

Financial Overview

• 1Q EPS $1.14 — up 28% from last year• Cash flow from operations of $138.1

million versus $97.8 million last year• Record adjusted claims of 142 million,

up 16% from last year• Record generic utilization of 54%

versus 49% last year• Gross profit per adjusted claim of $1.87

versus $1.77 last year (excluding non-recurring gain last year)

• Increased 2005 EPS guidance

Q1 2005 Highlights

25

Financial Overview

$0.00

$0.20

$0.40

$0.60

$0.80

$1.00

$1.20

$1.40

$1.60

Q1'01

Q2'01

Q3'01

Q4'01

Q1'02

Q2'02

Q3'02

Q4'02

Q1'03

Q2'03

Q3'03

Q4'03

Q1'04

Q2'04

Q3'04

Q4'04

Q1'05

Pe

r s

ha

re

EPS Free cash flow per share*

(1) Reflects a $70-$75 million reduction in Q2 2003 due to one-time impact of implementing a new wholesale purchase agreement

(2) Excludes a $0.10 per share charge for the early retirement of debt(3) Excludes a $0.20 charge to increase legal reserves for the cost of defense.

Quality of Earnings

(1)(1)(2)(2)

* Reflects a 12-month moving average of free cash flow (cash from operations less CapX)

(3)(3)

26

Components of EPS Growth — 2004

0%

5%

10%

15%

20%

25%

Express Scripts*

Rx Growth EBITDA/ Rx Growth Cap Structure/ Other

* Excluding $25 million charge to increase legal reserves for the cost of defense and $5.5 million termination payment received

6%6%

7%7%

8%8%

Financial Overview

$0.68

$0.80$0.88

$1.03

$1.12

$1.05

$0.50

$0.70

$0.90

$1.10

1999 2000 2001 2002 2003 2004**

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, www.express-scripts.com 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.

10.5% CAGR

28

Gross Profit/SGA/EBITDA per Adj. Rx

$0.50

$0.70

$0.90

$1.10

$1.30

$1.50

$1.70

$1.90

1999 2000 2001 2002 2003 2004*

Gross Profit per Adj Rx SGA per Adj Rx EBITDA per Adj Rx

Future EBITDA per Adj. Rx Must Come From Gross Profit per Adj. Rx•* Excluding $25 million charge to increase legal reserves for the cost of defense and $5.5 million termination payment received.

29

Focus on Return on Invested Capital (ROIC)

Express Scripts ROIC*

0%2%

4%6%

8%10%

12%14%

16%18%

20%

2000

2001

2002

2003

2004

**

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

30

Why Express Scripts? Industry-Leading ROIC

Comparison of Peer Group ROIC - 2004

0%

2%

4%

6%

8%

10%

12%

14%

16%

18%

20%

Expr

ess

Scri

pts

Cig

na

Wal

gree

ns

Car

emar

k

Aet

na

CVS

Med

co

Wel

lpoi

nt

We Lead Our Peer Group in ROIC Performance

Source: Express Scripts Analysis

31

Our Financial Goals

• 15% + EBITDA growth

• Increase gross profit per claim

• Maintain ROIC leadership 0%

5%

10%

15%

20%

25%

Express Scripts

EBITDA Growth Cap Structure/ Other

5%-7%5%-7%

14%-16%14%-16%

32

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