Filed by Express Scripts, Inc.
Pursuant to Rule 425 under the Securities Act of 1933

Subject Company: Caremark Rx, Inc.
Commission File No.: 001-14200

FOR IMMEDIATE RELEASE

Investor Contacts:		Media Contacts:
Edward Stiften,Chief Financial Officer		Steve Littlejohn, Vice President, Public Affairs
David Myers, Vice President, Investor Relations		(314) 702-7556
(314) 702-7173
		Joele Frank / Steve Frankel
		Joele Frank, Wilkinson Brimmer Katcher
		(212) 355-4449

Express Scripts Comments on Caremark/CVS HSR Announcement

St. Louis, December 20, 2006 — Express Scripts, Inc. (Nasdaq: ESRX) today issued the following statement related to the announcement by Caremark Rx, Inc., (NYSE: CMX):

“As we expected, the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act has expired for CVS Corporation (NYSE: CVS). We said on December 18^th that we anticipate the Express Scripts transaction with Caremark would be completed in the third quarter of 2007. The superior value of the Express Scripts offer for Caremark is clear as evidenced by the strong support of both Express Scripts and Caremark stockholders.

Based on today’s closing stock prices, the Express Scripts offer has a value of $60.68 per share, or $26.5 billion in the aggregate, and provides Caremark stockholders with a 21.5% premium to the current value of the CVS offer.”

About Express Scripts

     Express Scripts, Inc. is one of the largest PBM companies in North America, providing PBM services to over 50 million members. Express Scripts serves thousands of client groups, including managed-care organizations, insurance carriers, employers, third-party administrators, public sector, and union-sponsored benefit plans.

     Express Scripts provides integrated PBM services, including network-pharmacy claims processing, home delivery services, benefit-design consultation, drug-utilization review, formulary management, disease management, and medical- and drug-data analysis services. The Company also

distributes a full range of injectable and infusion biopharmaceutical products directly to patients or their physicians, and provides extensive cost-management and patient-care services.

     Express Scripts is headquartered in St. Louis, Missouri. More information can be found at www.express-scripts.com, which includes expanded investor information and resources.

Safe Harbor Statement

     This press release contains forward-looking statements, including, but not limited to, statements related to the Company’s plans, objectives, expectations (financial and otherwise) or intentions. Actual results may differ significantly from those projected or suggested in any forward-looking statements. Factors that may impact these forward-looking statements include but are not limited to:

	•		uncertainties associated with our acquisitions, which include integration risks and costs, uncertainties associated with client retention and repricing of client contracts, and uncertainties associated with the operations of acquired businesses
	•		costs and uncertainties of adverse results in litigation, including a number of pending class action cases that challenge certain of our business practices
	•		investigations of certain PBM practices and pharmaceutical pricing, marketing and distribution practices currently being conducted by the U.S. Attorney offices in Philadelphia and Boston, and by other regulatory agencies including the Department of Labor, and various state attorneys general
	•		changes in average wholesale prices (“AWP”), which could reduce prices and margins, including the impact of a proposed settlement in a class action case involving First DataBank, an AWP reporting service
	•		uncertainties regarding the implementation of the Medicare Part D prescription drug benefit, including the financial impact to us to the extent that we participate in the program on a risk-bearing basis, uncertainties of client or member losses to other providers under Medicare Part D, and increased regulatory risk
	•		uncertainties associated with U.S. Centers for Medicare & Medicaid’s (“CMS”) implementation of the Medicare Part B Competitive Acquisition Program (“CAP”), including the potential loss of clients/revenues to providers choosing to participate in the CAP
	•		our ability to maintain growth rates, or to control operating or capital costs
	•		continued pressure on margins resulting from client demands for lower prices, enhanced service offerings and/or higher service levels, and the possible termination of, or unfavorable modification to, contracts with key clients or providers
	•		competition in the PBM and specialty pharmacy industries, and our ability to consummate contract negotiations with prospective clients, as well as competition from new competitors offering services that may in whole or in part replace services that we now provide to our customers
	•		results in regulatory matters, the adoption of new legislation or regulations (including increased costs associated with compliance with new laws and regulations), more aggressive enforcement of existing legislation or regulations, or a change in the interpretation of existing legislation or regulations
	•		increased compliance relating to our contracts with the DoD TRICARE Management Activity and various state governments and agencies
	•		the possible loss, or adverse modification of the terms, of relationships with pharmaceutical manufacturers, or changes in pricing, discount or other practices of pharmaceutical manufacturers or interruption of the supply of any pharmaceutical products
	•		the possible loss, or adverse modification of the terms, of contracts with pharmacies in our retail pharmacy network
	•		the use and protection of the intellectual property we use in our business

	•		our leverage and debt service obligations, including the effect of certain covenants in our borrowing agreements
	•		our ability to continue to develop new products, services and delivery channels
	•		general developments in the health care industry, including the impact of increases in health care costs, changes in drug utilization and cost patterns and introductions of new drugs
	•		increase in credit risk relative to our clients due to adverse economic trends
	•		our ability to attract and retain qualified personnel
	•		other risks described from time to time in our filings with the SEC

Risks and uncertainties relating to the proposed transaction that may impact forward-looking statements include but are not limited to:

	•		Express Scripts and Caremark may not enter into any definitive agreement with respect to the proposed transaction
	•		required regulatory approvals may not be obtained in a timely manner, if at all
	•		the proposed transaction may not be consummated
	•		the anticipated benefits of the proposed transaction may not be realized
	•		the integration of Caremark’s operations with Express Scripts may be materially delayed or may be more costly or difficult than expected.
	•		the proposed transaction would materially increase leverage and debt service obligations, including the effect of certain covenants in any new borrowing agreements.

We do not undertake any obligation to release publicly any revisions to such forward-looking statements to reflect events or circumstances after the date hereof or to reflect the occurrence of unanticipated events.

Important Information

This material is not a substitute for the prospectus/proxy statement Express Scripts and Caremark would file with the Securities and Exchange Commission (“SEC”) if an agreement between Express Scripts and Caremark is reached or any other documents which Express Scripts may send to shareholders in connection with the proposed transaction. Investors are urged to read any such documents, when available, because they will contain important information. Such documents would be available free of charge at the SEC’s website (www.sec.gov) or by directing a request to Express Scripts, 13900 Riverport Dr., Maryland Heights, Missouri, Attn: Corporate Secretary, or MacKenzie Partners, Inc, at 800-322-2885 or by email at expressscripts@mackenziepartners.com.

Express Scripts and its directors, executive officers and other employees may be deemed to be participants in any solicitation of Express Scripts or Caremark shareholders in connection with the proposed transaction. Information about Express Scripts’ directors and executive officers is available in Express Scripts’ proxy statement, dated April 18, 2006, for its 2006 annual meeting of stockholders. Additional information about the interests of potential participants will be included in any proxy statement filed in connection with the proposed transaction.

This material relates to a business combination transaction with Caremark proposed by Express Scripts which may become the subject of a registration statement filed with the SEC. Investors and security holders are advised to read this document and all other applicable documents if and when they becomes available because they will include important information. Investors and security holders may obtain a free copy of any documents filed by Express Scripts with the SEC at the SEC’s website (www.sec.gov) or by directing a request to Express Scripts at the address set forth above or MacKenzie Partners, Inc. at the telephone number and email address set forth above.

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