Dear Shareholders:

I appreciate the opportunity to report to you about Merck's performance in 2003 and about significant actions we have taken to strengthen Merck and better position our Company for growth in 2004 and beyond.

In 2003, our earnings did not reach the double-digit growth we projected and believed we could achieve. We also terminated development of two products in late-phase clinical trials—discontinuing further study on a compound to treat depression because it failed to demonstrate efficacy, and halting further study of a compound to treat diabetes, due to findings of a rare form of malignant tumors in mice.

These events, while unwelcome, should not overshadow the one fundamental truth most important to Merck's future success: Merck's ability to discover novel medicines and bring to market true advances in patient care remains the bedrock principle on which Merck will conduct its business and is the key to the future success of our Company.

Our scientific capabilities; our talented and committed workforce; our experienced and involved Board of Directors; our dedication to the highest standards of ethical behavior; and our strict adherence to principles of good corporate governance have kept—and will continue to keep—Merck in the forefront of discovery, innovation and integrity.

As we envision the environment in which pharmaceutical companies will be operating in the years ahead, we believe— and we're hardly alone in this belief—that those companies that develop competitively priced, novel medicines that demonstrably improve the health and well-being of patients will prosper.

Merck has a long and distinguished record of scientific excellence, discovering drugs and vaccines that have literally transformed the practice of medicine and saved and improved the lives of millions. Our research and development efforts are the foundation of this Company and the engine of its future growth. We will continue to invest in the discovery and development of the novel medicines that have defined success at Merck and are confident that these investments will lead to future growth.

To support that commitment, we took significant actions in 2003 to strengthen our Company for the future:

• We completed the successful spin-off of Medco Health Solutions, Inc., in August. This spin-off has not only brought value to our shareholders, it also has sharpened Merck's focus as a pure pharmaceutical research company.
• We increased Merck's ownership of Tokyo-based Banyu Pharmaceutical Co., Ltd., from 51 percent to 99.4 percent, through two tender offers. This action further strengthened Merck's position in Japan, the world's second-largest pharmaceutical market.
• We announced the elimination of 4,400 positions worldwide as part of our effort to fundamentally lower our cost structure and improve the efficiency of our operations.
• And, in the last half of 2003, we submitted New Drug Applications (NDAs) for Vytorin, the ezetimibe/simvastatin combination, and Arcoxia to the U.S. Food and Drug Administration (FDA) for approval.

Vytorin (which is a result of our partnership with Schering-Plough) is expected to be the first product to reduce cholesterol by targeting both its absorption in the intestine and its production in the liver. This represents a new approach to treating high cholesterol, a true innovation in patient care. The FDA accepted the filing for standard review in November.

Arcoxia, Merck's newest coxib, has already been launched successfully in 38 countries around the world. Merck's NDA for Arcoxia seeks approval for three indications that no other coxib in the United States currently has–chronic low back pain, acute gouty arthritis and ankylosing spondylitis (a painful condition of the spine). We are awaiting notification from the FDA regarding the acceptance of our filing.

Both of these products have significant sales potential and we expect them to make substantial contributions to earnings.

We ended 2003 as a much stronger Company as a result of our actions, better positioned to draw on what has always made Merck uniquely successful—a commitment to developing novel medicines that will deliver true advances in patient care. This commitment, when combined with our actions to reduce costs and maximize earnings, has positioned Merck to succeed in the long term.

Of course, to succeed in the long term, we must first succeed in the near term. The strength of our existing product franchises, their positions in the market, and the steps we have taken to contain costs and increase efficiency, will drive our near-term growth.

• Each of our key product franchises ranks either No. 1 or 2 in worldwide sales in large and growing markets. We continue to reinforce our strong competitive position through ongoing clinical and outcomes studies that broaden indications and drive continued growth.
• Our competitive position is further reinforced by the strong relationships we have built with our managed care customers. These relationships stem from Merck's ability to work with managed care in a way that brings value to payers and patients alike. With our top 31 customers—who represent about 90 percent of the managed care universe–products such as Vioxx, Fosamax, Singulair, Cozaar and Zocor hold exclusive or co-preferred positions on their formularies in the vast majority of cases.
• We are reducing our cost of doing business without sacrificing research, manufacturing quality, or our support for our sales and marketing efforts. We are ensuring that our operations run as efficiently and economically as possible. The savings we have identified and are implementing, including the reduction in the size of our workforce, will begin benefiting our bottom line in 2004 and are expected to generate annual savings of $250 to $300 million in 2005 in payroll and benefits.
• We are using our capital as efficiently as possible. Through such efforts as reducing inventories, streamlining our supply chain, making optimal use of our manufacturing capacity, and reducing the costs of capital projects, we expect to free up approximately $600 million in additional cash flow through 2006.

All of these actions are part of the strong financial position Merck enjoys (and which is detailed elsewhere in this report) and are expected to contribute to growth in our earnings per share in the next several years, as Merck becomes a more efficient operation.

In June 2006, the U.S. market exclusivity for Zocor, which has been an important contributor to our earnings, will expire. Patent expirations are a fact of life in this industry, and their timing and impact are somewhat predictable. The true measure of our success in meeting this challenge is our ability to bring new products to market that provide true clinical benefit at a competitive price. It is a challenge we are ready to meet.

In the second half of 2004, we expect to submit an application for ProQuad to the FDA. ProQuad adds chickenpox vaccine to the existing measles, mumps and rubella vaccine, potentially increasing the number of children who will be vaccinated against chickenpox.

In 2005, we expect to file applications for three other vaccines that hold significant promise to help prevent: human papillomavirus, a primary cause of cervical cancer; rotavirus, a highly contagious virus that is the most common cause of gastroenteritis in infants and young children, and which causes the hospitalization of at least 50,000 American children under the age of 5 every year; and, the pain associated with shingles, the reactivation of the chickenpox virus that afflicts 1 million adults every year in the United States.

If ongoing trials are successful, in 2006 we anticipate filing for approval for a DP-IV inhibitor for diabetes. Early tests have demonstrated that the product does not lead to weight gain and does not produce edema. Additional studies to confirm these findings are under way. With 5 percent of the U.S. population living with diabetes, it would be a welcome addition to our product line.

Our early-stage pipeline also shows strong promise. Merck scientists are working in a significant number of disease areas to treat such ailments as Alzheimer's disease, obesity, respiratory disease, coronary heart disease and rheumatoid arthritis. In addition to working in these important areas, we are also working on novel and effective approaches to accelerating drug development and improving the probability of success of our internal R&D efforts. These efforts will maximize our research investment at every stage of the pipeline.

While we are enhancing our internal research capabilities, we are mindful that other pharmaceutical and biotechfirms are also doing valuable scientific work. That is why we have expanded our approach to external collaborations and relationships. This effort has made a real difference.

In 1999, for example, we completed just 10 deals with external partners. In 2003, we closed on 47 significant transactions, including research collaborations, preclinical and clinical compounds, and technology transactions. Approximately 70 potential opportunities are in detailed review. We are pursuing partnerships across the entire continuum of scientific possibilities—from early research to late-stage development. They add value to our pipeline and should contribute to our growth.

Some have suggested that Merck should look beyond partnerships and alliances and consider a major merger with another pharmaceutical company. We have consistently pursued external alliances that make sense long term for Merck and its shareholders. Our partnership with Schering-Plough on Zetia and now on Vytorin, and our most recent alliances with such firms as Lundbeck, GenPath, Neurogen, Amrad and Actelion are all good examples of external alliances that make sense for Merck.

When looking at a large-scale merger, with all that entails, we have to be certain that it would bring significant additions to our pipeline and would add to long-term growth. It would have to, in short, meet the same criteria we use to evaluate any potential licensing or acquisition opportunity. We have consistently found that a large-scale acquisition or merger does not meet those criteria, providing instead the possibility of a short-term gain at the expense of long-term growth. That's not an appropriate trade-off, not just because of how it would affect our ability to meet our long-term goals, but because it could also compromise the values that have long made Merck a success, not only for its shareholders, but also for those who rely on its products, as well as for the larger community.

In 2003, Merck continued to honor its long-standing responsibilities as a good corporate citizen.

• Through our Patient Assistance Program, we filled more than 5.6 million prescriptions for more than 600,000 Americans who otherwise would not have been able to afford them.
• In keeping with our ongoing commitment to promoting access to essential medicines for people in need, we recently announced that we will provide our medicines free for low-income Medicare beneficiaries who exhaust their $600 transitional assistance allowance in Medicare-endorsed drug discount cards.
• Our partnership with the Bill & Melinda Gates Foundation and the government of Botswana continues to bring hope and healing to people in that country living with HIV and their families and communities.
• Our commitment to the highest standards of ethical behavior was given the best possible ranking by Management & Excellence and Rating Research LLC, two respected corporate ethics rating organizations.
• And in December, Merck was honored by the U.S. Secretary of Commerce and the U.S. Chamber of Commerce with their first Corporate Stewardship Award. The award was presented to a small, medium and large business that "balances their responsibilities to their employees and shareholders with their responsibilities to their communities."

To help ensure access to medicines for America's seniors and the disabled, Merck was an unwavering supporter of the new Medicare prescription drug benefit, which President Bush signed into law late last year. This expansion of Medicare supports pharmaceutical innovation because it is based on competition. As more seniors—as many as 12 million more—have greater access to prescription drugs through Medicare, we will have the opportunity to compete to broaden our customer base. Based on our proven track record in both securing formulary access and in increasing our market share in managed care, we are well-positioned for this competition.

We are pursuing the strategy that is right for Merck and in the best interests of you, our shareholders. The ways in which we met the challenges of 2003, coupled with last year's accomplishments, have made Merck a stronger and more focused company—one that is well-positioned to compete in the new environment. Continuing to focus on developing and launching novel medicines and vaccines backed by proven outcomes at competitive prices, aggressively pursuing external alliances, lowering our cost structure, and maximizing our in-line franchises will allow us to grow and succeed over the long term.

While some of the actions we took last year were difficult—especially the announcement of the elimination of 4,400 positions—they strengthened the Company and will increase our competitiveness going forward. By building on our strengths, we will meet the challenges of the years ahead while contributing, as we always have, to the health and well-being of people around the world by honoring our commitment to true advances in patient care.

Raymond V. Gilmartin
Chairman, President and Chief Executive Officer
March 1, 2004