MERCK & CO INC
10-K405, 1999-03-24
PHARMACEUTICAL PREPARATIONS
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<PAGE>
 
    As filed with the Securities and Exchange Commission on March 24, 1999
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                      SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D. C. 20549
 
                               ----------------
 
                                   FORM 10-K
 
(MARK ONE)
<TABLE>
 <C>     <S>
         Annual Report Pursuant to Section 13 or 15(d) of the Securities
     [X] Exchange Act of 1934
         For the Fiscal Year Ended December 31, 1998
 
                                      or
 
         Transition Report Pursuant to Section 13 or 15(d) of the Securities
     [_] Exchange Act of 1934
         For the transition period from ______ to ______
</TABLE>
 
                          Commission File No. 1-3305
 
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                               MERCK & CO., INC.
 
                                One Merck Drive
                     Whitehouse Station, N. J. 08889-0100
                                (908) 423-1000
 
        Incorporated in New Jersey                  I.R.S. Employer
                                             Identification No. 22-1109110
 
          Securities Registered pursuant to Section 12(b) of the Act:
 
                                                 Name of Each Exchange
           Title of Each Class                    on which Registered
               Common Stock                 New York and Philadelphia Stock
            ($0.01 par value)                         Exchanges
 
   Number of shares of Common Stock ($0.01 par value) outstanding as of
February 26, 1999:  2,362,986,851.
 
   Aggregate market value of Common Stock ($0.01 par value) held by non-
affiliates on December 31, 1998 based on closing price on February 26,
1999: $192,283,000,000.
 
   Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports), and (2) has been subject to
such filing requirements for the past 90 days. Yes [X] No [_]
 
   Indicate by check mark if disclosure of delinquent filers pursuant to Item
405 of Regulation S-K is not contained herein, and will not be contained, to
the best of registrant's knowledge, in definitive proxy or information
statements incorporated by reference in Part III of this Form 10-K or any
amendment to this Form 10-K. [X]
 
                     Documents Incorporated by Reference:
 
                 Document                          Part of Form 10-K
    Annual Report to stockholders for                Parts I and II
            the fiscal year
         ended December 31, 1998
      Proxy Statement for the Annual                    Part III
              Meeting of
    Stockholders to be held April 27,
                 1999
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<PAGE>
 
                                     PART I
 
Item 1. Business.
 
   Merck & Co., Inc. (the "Company") is a global research-driven pharmaceutical
company that discovers, develops, manufactures and markets a broad range of
human and animal health products, directly and through its joint ventures, and
provides pharmaceutical benefit services through Merck-Medco Managed Care,
L.L.C. ("Merck-Medco"). The Company's operations are principally managed on a
products and services basis and are comprised of two reportable segments: Merck
Pharmaceutical and Merck-Medco. Merck Pharmaceutical products consist of
therapeutic agents, sold by prescription, for the treatment of human disorders.
Merck-Medco revenues are derived from the filling and management of
prescriptions and health management programs.
 
   The following table shows the sales of various categories of the Company's
products and services:
 
<TABLE>
<CAPTION>
   ($ in millions)                                  1998      1997      1996
   ---------------                                --------- --------- ---------
   <S>                                            <C>       <C>       <C>
   Elevated cholesterol.......................... $ 4,694.1 $ 4,672.3 $ 4,055.9
   Hypertension/heart failure....................   4,213.5   3,855.0   3,452.6
   Anti-ulcerants................................   1,113.5   1,184.4   1,033.5
   Vaccines/biologicals..........................     846.7     733.6     586.8
   Osteoporosis..................................     775.2     532.1     281.8
   Antibiotics...................................     743.3     774.9     822.3
   Human immunodeficiency virus ("HIV")..........     676.3     581.7     187.8
   Ophthalmologicals.............................     630.7     639.1     643.6
   Animal health/crop protection.................       --      550.0   1,044.1
   Other Merck products..........................   1,603.2     673.5     562.3
   Merck-Medco...................................  11,601.7   9,440.3   7,158.0
                                                  --------- --------- ---------
     Total....................................... $26,898.2 $23,636.9 $19,828.7
                                                  ========= ========= =========
</TABLE>
 
   Human health products include therapeutic agents within the Merck
Pharmaceutical segment, sold by prescription for the treatment of human
disorders, as well as preventive agents (vaccines/biologicals). Among these are
elevated cholesterol products, which include Zocor (simvastatin) and Mevacor
(lovastatin); hypertension/heart failure products which include Vasotec
(enalapril maleate), the largest-selling product among this group, Cozaar
(losartan potassium), Hyzaar (losartan potassium and hydrochlorothiazide),
Prinivil (lisinopril) and Vaseretic (enalapril maleate and
hydrochlorothiazide); anti-ulcerants, of which Pepcid (famotidine) is the
largest-selling; vaccines/biologicals, of which M-M-R II (measles, mumps and
rubella virus vaccine live), Recombivax HB (hepatitis B vaccine [recombinant])
and Varivax (varicella virus vaccine live [Oka/Merck]), a live virus vaccine
for the prevention of chickenpox, are the largest-selling; osteoporosis, which
is comprised of Fosamax (alendronate sodium), for treatment and prevention in
postmenopausal women; antibiotics, of which Primaxin (imipenem and cilastatin
sodium) and Noroxin (norfloxacin) are the largest-selling; human
immunodeficiency virus, which includes Crixivan (indinavir sulfate), a protease
inhibitor for the treatment of human immunodeficiency viral infection in
adults; and ophthalmologicals, of which Timoptic (timolol maleate), Timoptic-XE
(timolol maleate ophthalmic gel forming solution) and Trusopt (dorzolamide
hydrochloride) are the largest selling.
 
   Animal health products include medicinals used to control and alleviate
disease in livestock, small animals and poultry. Crop protection includes
products for the control of crop pests and fungal disease. In July 1997, the
Company sold its crop protection business to Novartis. In August 1997, the
Company and Rhone-Poulenc combined their animal health and poultry genetics
businesses to form Merial Limited ("Merial"). Amounts for 1997 reflect sales
for these businesses prior to the completion of these transactions.
 
                                       2
<PAGE>
 
   Other Merck products include sales of Proscar (finasteride), which provides
long-term disease management of symptomatic benign prostate enlargement
("BPH"), Singulair (montelukast sodium), for the prevention and chronic
treatment of asthma in adults and children aged six years and above, Maxalt
(rizatriptan benzoate), an anti-migraine treatment, Propecia (finasteride),
which treats male pattern hair loss and Aggrastat (tirofiban hydrochloride), a
platelet blocker, for treatment of acute coronary syndrome, and other human
pharmaceuticals within the Merck Pharmaceutical segment, continuing sales to
divested businesses, pharmaceutical and animal health supply sales to the
Company's joint ventures and, as of July 1, 1998, supply sales to Astra
Pharmaceuticals, L.P. Also included in this category are rebates and discounts
on Company pharmaceutical products.
 
   Merck-Medco primarily includes Merck-Medco sales of non-Merck products and
Merck-Medco pharmaceutical benefit services, principally managed prescription
drug programs and programs to help manage patient health.
 
   In 1997, the Company acquired Istituto Gentili S.p.A., a privately-held
Italian pharmaceutical company that owned the intellectual property rights for
alendronate, which is marketed in the United States by the Company as Fosamax.
 
   Propecia, which treats male pattern hair loss, was introduced in the United
States and 11 other countries in 1998, with launches pending in 13 more. In
1998 and through February 1999, Cozaar received regulatory approval for a new
heart failure indication in 16 countries, bringing the number of countries
that have approved this indication to 18, and approvals are pending in other
markets. In February 1998, the U.S. Food and Drug Administration ("FDA")
cleared Singulair, a once-a-day oral leukotriene D4 receptor antagonist, for
marketing in the United States for the prevention and chronic treatment of
asthma in adults and children aged six years and above. Singulair has now been
launched in 38 countries including the United States, the United Kingdom,
Spain, Germany, Sweden and Denmark. In March 1998, the FDA granted traditional
approval for Crixivan in combination with antiretroviral agents for the
treatment of HIV infection (in 1996, the FDA granted an accelerated approval
for Crixivan for treatment of HIV infection). In March 1999, the FDA approved
a new 333 mg capsule strength of Crixivan and a new unit dose (blister)
package for existing 400 mg capsules. In March 1998, the FDA cleared Proscar
for marketing to reduce the need for BPH-related surgery and the risk of
developing acute urinary retention. In April 1998, the FDA approved an
expanded indication for Zocor to reduce the risk of first stroke or transient
ischemic attack in people with high cholesterol and coronary heart disease. In
July 1998, the FDA approved an 80 mg tablet of Zocor. In addition, the
prescribing information for Zocor in the United States has been changed to
recommend the 20 mg tablet as the usual starting dose. In April 1998, the FDA
granted marketing clearance for Cosopt (dorzolamide hydrochloride and timolol
maleate ophthalmic solution), which is indicated for the reduction of elevated
intraocular pressure in patients who do not respond adequately to beta-
blockers alone. In May 1998, the FDA approved Aggrastat, a platelet blocker,
for marketing in the United States for the treatment of acute coronary
syndrome, including patients with unstable angina/non-Q-wave myocardial
infarction who are managed medically and those undergoing angioplasty or
atherectomy. Aggrastat has been launched in eight countries, including the
United States, Switzerland, Germany and Mexico. In June 1998, the FDA approved
for marketing in the United States, Maxalt, a new oral anti-migraine
treatment. Maxalt is now marketed in 11 countries, including the United
States, the United Kingdom, Sweden, the Netherlands and Mexico. In February
1999, Mexico became the first country to grant marketing clearance to Vioxx
(rofecoxib), a once-daily, anti-inflammatory COX-2 specific inhibitor for the
treatment of osteoarthritis and relief of pain, and other regulatory approvals
are pending worldwide, including in the United States where the Company filed
a New Drug Application ("NDA") with the FDA on November 23, 1998. On January
11, 1999, the FDA assigned a six-month priority review to the Company's NDA
for Vioxx. In February 1999, the Company received confirmation that the FDA's
Arthritis Advisory Committee meeting for Vioxx has been scheduled for April
20, 1999. In March 1999, the FDA approved a new use for Mevacor to reduce the
risk of first heart attack, unstable angina and coronary revascularization
procedures in people without symptoms of cardiovascular disease, with average
to moderately elevated levels of total and LDL cholesterol and below average
HDL cholesterol.
 
   Divestitures -- In July 1997, the Company sold its crop protection business
to Novartis for $910.0 million.
 
                                       3
<PAGE>
 
   In July 1998, the Company sold its one-half interest in The Dupont Merck
Pharmaceutical Company, its joint venture with E.I. du Pont de Nemours and
Company ("DuPont"), to DuPont for $2.6 billion in cash.
 
   These businesses were not significant to the Company's financial position,
liquidity or results of operations.
 
   Joint Venture -- In 1982, the Company entered into an agreement with Astra
AB ("Astra") to develop and market Astra products in the United States. In
1993, the Company's total sales of Astra products reached a level that
triggered the first step in the establishment of a joint venture business
carried on by Astra Merck Inc. ("AMI"), in which the Company and Astra each
owned a 50% share. The joint venture, formed in November 1994, developed and
marketed most of Astra's new prescription medicines in the United States. Joint
venture sales consisted primarily of Prilosec (omeprazole), the first of a
class of medications known as proton pump inhibitors which slows the production
of acid from the cells of the stomach lining. In December 1996, the FDA cleared
Prilosec for use as initial therapy in the treatment of heartburn and other
symptoms associated with gastroesophageal reflux disease.
 
   On July 1, 1998, the Company and Astra completed the restructuring of the
ownership and operations of the joint venture whereby the Company acquired
Astra's interest in AMI, renamed KBI Inc. ("KBI"), for consideration totaling
$3.1 billion. KBI's net operating assets, excluding certain product rights,
were then combined with the net assets of Astra's wholly owned subsidiary,
Astra USA, Inc., to form a new U.S. limited partnership named Astra
Pharmaceuticals, L.P. in which the Company maintains a limited partner
interest. For a franchise fee payment of $230.0 million, the partnership became
the exclusive distributor of the products for which KBI retained rights. The
Company earns certain partnership returns as well as ongoing revenue based on
sales of current and future KBI products. The partnership returns include a
priority return, a fixed return and certain variable returns which are based,
in part, upon sales of certain former Astra USA, Inc. products. The fixed
return represents accretion of the carrying value of the Company's limited
partnership interest from its initial carrying value up to its liquidating net
worth, which is being recognized into income over 10 years on a straight-line
basis. For a payment of $443.0 million, Astra purchased an option to buy the
Company's interest in the KBI products in 2008, 2012 or 2016, excluding the
Company's interest in the gastrointestinal medicines Prilosec and perprazole.
 
   In December 1998, Astra announced plans to merge with Zeneca Group Plc. If
this proposed merger is completed, Astra will be required to make one-time
payments to the Company totaling approximately $1.8 billion for the
relinquishment of certain rights, including option rights to future Astra
products with no existing or pending U.S. patents at the time of the merger.
This merger would also trigger a partial redemption of the Company's limited
partnership interest in 2008. Furthermore, upon completion of the merger,
Astra's option to buy the Company's interest in the KBI products would be
exercisable only in 2010 and the Company would obtain the right to require
Astra to purchase such interest in 2008.
 
   In 1989, the Company formed a joint venture with Johnson & Johnson to
develop, market and manufacture consumer healthcare products in the United
States. In April 1995, the joint venture obtained FDA clearance in the United
States for marketing Pepcid AC (famotidine), an over-the-counter form of the
Company's ulcer medication Pepcid. This 50% owned joint venture was expanded
into Europe in 1993, and Canada in 1996. The European extension currently
markets and sells over-the-counter pharmaceutical products in France, Germany,
Italy, Spain and the United Kingdom.
 
   In 1991, the Company and DuPont entered into a joint venture to form a
worldwide pharmaceutical company for the research, marketing, manufacturing and
sale of pharmaceutical and imaging agent products. DuPont contributed its
entire worldwide pharmaceutical and radiopharmaceutical imaging agents
businesses and provided administrative services. The Company contributed cash
and European marketing rights to several of its prescription medicines and
provided research and development and international industry expertise. In
January 1995, the joint venture began co-promotion of the Company's
prescription medicines, Prinivil and Prinzide (lisinopril and
hydrochlorothiazide), in the United States. As discussed above under
"Divestitures," in July 1998, the Company sold its one-half interest in the
joint venture to DuPont for $2.6 billion in cash.
 
                                       4
<PAGE>
 
   Effective April 1992, the Company, through the Merck Vaccine Division, and
Connaught Laboratories, Inc. ("Connaught"), recently renamed Pasteur Merieux
Connaught USA ("PMC USA"), an affiliate of Pasteur Merieux Connaught ("PMC"),
which is part of the Rhone-Poulenc group, agreed to collaborate on the
development and marketing of combination pediatric vaccines and to promote
selected vaccines in the United States. The research and marketing
collaboration enables the companies to pool their resources to expedite the
development of vaccines combining several different antigens to protect
children against a variety of diseases, including Haemophilus influenzae type
b, hepatitis B, diphtheria, tetanus, pertussis and poliomyelitis.
 
   In 1994, the Company, through the Merck Vaccine Division, and PMC formed a
joint venture to market human vaccines and to collaborate in the development of
new combination vaccines for distribution in the European Union ("EU") and the
European Free Trade Association. The Company and PMC contributed, among other
things, their European vaccine businesses for equal shares in the joint
venture, known as Pasteur Merieux MSD, S.N.C. The joint venture is subject to
monitoring by the EU, to which the partners made certain undertakings in return
for an exemption from European Competition Law, effective until December 2006.
The joint venture is active through affiliates in Belgium, Denmark, Italy,
Germany, Spain and the United Kingdom, and through distributors throughout the
rest of Europe.
 
   In 1995, Merck-Medco entered into a joint venture with Wyeth-Ayerst
Laboratories, a division of American Home Products Corporation, to develop,
market and implement health management programs for certain conditions,
including several involving women's health. This joint venture was dissolved by
the parties effective February 1999.
 
   In April 1997, the Company and Chugai Pharmaceutical Co., Ltd. completed
arrangements relating to the formation of a joint venture, Chugai MSD Co., Ltd.
("Chugai MSD"), which was created for the development and marketing of self-
medication pharmaceutical products in Japan. Products currently marketed by
Chugai MSD include the Chugai Ichoyaku line of gastrointestinal products, and
Efeel, a famotidine product for stomach pain, nausea, heartburn and
indigestion, which is marketed in the United States, Canada and various
European markets by the Johnson & Johnson Merck Consumer Pharmaceuticals Co.
joint venture under the trademark Pepcid AC.
 
   In August 1997, the Company and Rhone-Poulenc combined their respective
animal health and poultry genetics businesses to form Merial, a fully-
integrated, stand-alone joint venture, equally owned by the Company and Rhone-
Poulenc. Merial is the world's largest company dedicated to the discovery,
manufacture and marketing of veterinary pharmaceuticals and vaccines. The
Company contributed developmental research personnel, sales and marketing
activities, and animal health products, as well as its poultry genetics
business. Rhone-Poulenc contributed research and development, manufacturing,
sales and marketing activities, and animal health products, as well as its
poultry genetics business.
 
   Competition -- The markets in which the Company's pharmaceutical business is
conducted are highly competitive and, in many cases, highly regulated. Such
competition involves an intensive search for technological innovations and the
ability to market these innovations effectively. With its long-standing
emphasis on research and development, the Company is well prepared to compete
in the search for technological innovations. Additional resources to meet
competition include quality control, flexibility to meet exact customer
specifications, an efficient distribution system and a strong technical
information service. The Company is active in acquiring and marketing products
through joint ventures and licenses and has been expanding its sales and
marketing efforts to further address changing industry conditions. However, the
introduction of new products and processes by competitors may result in price
reductions and product replacements, even for products protected by patents.
For example, the number of compounds available to treat diseases typically
increases over time and has resulted in slowing the growth in sales of certain
of the Company's products.
 
   In addition, particularly in the area of human pharmaceutical products,
legislation enacted in all states allows, encourages or, in a few instances, in
the absence of specific instructions from the prescribing physician,
 
                                       5
<PAGE>
 
mandates the use of "generic" products (those containing the same active
chemical as an innovator's product) rather than "brand-name" products.
Governmental and other pressures toward the dispensing of generic products have
significantly reduced the sales of certain of the Company's products no longer
protected by patents, such as Moduretic (amiloride HCl and
hydrochlorothiazide), Clinoril (sulindac) and Aldomet (methyldopa), and slowed
the growth of certain other products.
 
   See also the description of the effect upon competition of the Drug Price
Competition and Patent Term Restoration Act of 1984 ("PTRA") on page 8.
 
   It is generally the Company's position to limit the net weighted average
price changes for all human health products in the United States to the
projected general rate of inflation as measured by the U.S. Consumer Price
Index, given stable markets and government policies that foster innovation.
 
   Merck-Medco's pharmacy benefit management business is highly competitive.
Merck-Medco competes with other pharmacy benefit managers, insurance companies
and other providers of health care and/or administrators of healthcare
programs. Merck-Medco competes primarily on the basis of its ability to design
and administer innovative programs that help plan sponsors provide high-
quality, affordable prescription drug care and health management services to
health plan members. Merck-Medco dispenses prescription drugs from its national
network of mail service pharmacies, manages prescriptions dispensed through a
national network of participating retail pharmacies and implements health
management programs to help its clients provide better care for patients with
high-cost, high-risk conditions.
 
   Distribution -- The Company sells its human health products to drug
wholesalers and retailers, hospitals, clinics, government agencies and managed
healthcare providers such as health maintenance organizations and other
institutions. The Company's professional representatives communicate the
effectiveness, safety and value of the Company's products to healthcare
professionals in private practice, group practices and managed-care
organizations. Merck-Medco sells its pharmaceutical benefit management services
to corporations, labor unions, insurance companies, Blue Cross/Blue Shield
organizations, government agencies, federal and state employee plans, health
maintenance and other similar organizations.
 
   Raw Materials -- Raw materials and supplies are normally available in
quantities adequate to meet the needs of the Company's business.
 
   Government Regulation and Investigation -- The pharmaceutical industry is
subject to global regulation by regional, country, state and local agencies. Of
particular importance is the FDA in the United States, which administers
requirements covering the testing, approval, safety, effectiveness,
manufacturing, labeling and marketing of prescription pharmaceuticals. In many
cases, the FDA requirements have increased the amount of time and money
necessary to develop new products and bring them to market in the United
States. In 1997, the Food and Drug Administration Modernization Act was passed
and was the culmination of a comprehensive legislative reform effort designed
to streamline regulatory procedures within the FDA and to improve the
regulation of drugs, medical devices, and food. The legislation was principally
designed to ensure the timely availability of safe and effective drugs and
biologics by expediting the premarket review process for new products. A key
provision of the legislation is the re-authorization of the Prescription Drug
User Fee Act of 1992, which permits the continued collection of user fees from
prescription drug manufacturers to augment FDA resources earmarked for the
review of human drug applications. This helps provide the resources necessary
to ensure the prompt approval of safe and effective new drugs.
 
   In recent years, an increasing number of legislative proposals have been
introduced or proposed in Congress and in some state legislatures that would
effect major changes in the healthcare system, either nationally or at the
state level. Although a reform bill has not been enacted at the federal level,
some states have passed reform legislation and further federal and state
developments are expected. Although the Company is well positioned to respond
to evolving market forces, it cannot predict the outcome or effect of
legislation resulting from these reform efforts.
 
                                       6
<PAGE>
 
   For many years, the pharmaceutical industry and the pharmacy benefits
management business has been under federal and state oversight with the new
drug approval system, drug safety, advertising and promotion, drug purchasing
and reimbursement programs and formularies variously under review. The Company
believes that it will continue to be able to conduct its operations, including
the introduction of new drugs to the market, in this regulatory environment.
One type of federal initiative to contain federal healthcare spending is the
prospective or "capitated" payment system, first implemented to reduce the rate
of growth in Medicare reimbursement to hospitals. Such a system establishes in
advance a flat rate for reimbursement for health care for those patients for
whom the payer is fiscally responsible. This type of payment system and other
cost containment systems are now widely used by public and private payers and
have caused hospitals, health maintenance organizations and other customers of
the Company to be more cost-conscious in their treatment decisions, including
decisions regarding the medicines to be made available to their patients. The
Company continues to work with private and federal employers to slow increases
in healthcare costs. Further, the Company's efforts to demonstrate that its
medicines can help save costs in other areas, and pricing flexibility across
its product portfolio, have encouraged the use of the Company's medicines and
have helped offset the effects of increasing cost pressures.
 
   Also, federal and state governments have pursued methods to directly reduce
the cost of drugs for which they pay. For example, federal legislation enacted
in 1990 requires the Company to pay a specified rebate for medicines reimbursed
by Medicaid. Federal legislation enacted in 1992 mandates the payment of
rebates similar to the Medicaid rebate for outpatient medicines purchased by
certain Public Health Service entities and "disproportionate share" hospitals
(hospitals meeting certain criteria). That same law mandates minimum discounts
of 24% off of a defined "non-federal average manufacturer price" for the
Veterans' Administration, Federal Supply Schedule and certain other federal
sector purchasers of medicines.
 
   The Omnibus Budget Reconciliation Act of 1993 established a new Federal
Vaccines for Children entitlement program, under which the U.S. Centers for
Disease Control and Prevention ("CDC") funds and purchases recommended
pediatric vaccines at a capped public sector price for the immunization of
Medicaid-eligible, uninsured, native American and certain underinsured
children. The Company was awarded eight CDC contracts in 1998 for the supply of
its pediatric vaccines for this program.
 
   The Company encounters similar regulatory and legislative issues in most of
the foreign countries where it does business. There, too, the primary thrust of
governmental inquiry and action is toward determining drug safety and
effectiveness, often with mechanisms for controlling the prices of prescription
drugs and the profits of prescription drug companies. The EU has adopted
directives concerning the classification, labeling, advertising, wholesale
distribution and approval for marketing of medicinal products for human use.
The Company's policies and procedures are already consistent with the substance
of these directives; consequently, it is believed that they will not have any
material effect on the Company's business.
 
   In addition, countries within the EU, recognizing the economic importance of
the research-based pharmaceutical industry and the value of innovative
medicines, are working with industry and the European Commission on proposals
for market deregulation.
 
   The Company is subject to the jurisdiction of various regulatory agencies
and is, therefore, subject to potential administrative actions. Such actions
may include seizures of products and other civil and criminal sanctions. Under
certain circumstances, the Company on its own may deem it advisable to initiate
product recalls. Although it is difficult to predict the ultimate effect of
these activities and legislative, administrative and regulatory requirements
and proposals, the Company believes that its development of new and improved
products should enable it to compete effectively within this environment.
 
   There are extensive federal and state regulations applicable to the practice
of pharmacy and the administration of managed healthcare programs. Each state
in which Merck-Medco operates a pharmacy has laws and regulations governing its
operation and the licensing of and standards of professional practice by its
 
                                       7
<PAGE>
 
pharmacists. These regulations are issued by an administrative body in each
state (typically, a pharmacy board), which is empowered to impose sanctions for
noncompliance. The policies and procedures of the Company comply with these
regulations.
 
   Patents, Trademarks and Licenses -- Patent protection is considered, in the
aggregate, to be of material importance in the Company's marketing of human
health products in the United States and in most major foreign markets. Patents
may cover products per se, pharmaceutical formulations, processes for or
intermediates useful in the manufacture of products or the uses of products.
Protection for individual products extends for varying periods in accordance
with the date of grant and the legal life of patents in the various countries.
The protection afforded, which may also vary from country to country, depends
upon the type of patent and its scope of coverage.
 
   Patent portfolios developed for products introduced by the Company normally
provide marketing exclusivity. Patents are in effect for the following major
products in the United States: Aggrastat, Cosopt, Chibroxin (norfloxacin),
Cozaar, Crixivan, Fosamax, Hyzaar, Maxalt, Mefoxin (cefoxitin sodium), Mevacor,
Noroxin, PedvaxHIB (Haemophilus b conjugate vaccine), Pepcid, Primaxin,
Prinivil, Prinzide, Propecia, Proscar, Recombivax HB, Sinemet CR (carbidopa and
levodopa), Singulair, Timoptic-XE, Trusopt, Vaseretic, Vasotec, Zocor and
Prilosec (which was developed jointly by the Company and Astra and is supplied
exclusively to Astra Pharmaceuticals, L.P.). The lisinopril products (which
include Prinivil) and Sinemet CR are subject to agreements with third parties
and are not marketed exclusively by the Company.
 
   Several products will face expiration of product patents in the United
States and other countries in the near term, including Pepcid (U.S. - 2000),
Vasotec (U.S. - 2000), Mevacor (U.S. - 2001), Prinivil/Prinzide (U.S. - 2001)
and Vaseretic (U.S. - 2001). In addition, Prilosec will face expiration of a
product patent in 2001. In the aggregate, domestic sales of these products
represent 22% of the Company's human health sales for 1998. The Company expects
a significant decline in these sales in the years 2000 through 2002 upon the
loss of market exclusivity. With the exception of Prilosec, for which the
Company has U.S. rights only, a decline is also expected in the Company's
European sales for these products in the years 2000 through 2005 upon the loss
of market exclusivity in European countries throughout this period. These sales
represent 7% of the Company's human health sales for 1998.
 
   Product patent protection in the United States has expired for the following
human and animal pharmaceutical products: Aldomet, Aldoril (methyldopa and
hydrochlorothiazide), Amprol (amprolium), Blocadren (timolol maleate),
Clinoril, Decadron (dexamethasone), Diuril (chlorothiazide), Dolobid
(diflunisal), Flexeril (cyclobenzaprine hydrochloride), HydroDiuril
(hydrochlorothiazide), Indocin (indomethacin), Ivomec (ivermectin), certain
ivermectin-containing animal health products, Moduretic, Sinemet (carbidopa and
levodopa), TBZ and Thibenzole (thiabendazole), Timoptic and Timolide (timolol
maleate and hydrochlorothiazide).
 
   While the expiration of a product patent normally results in the loss of
market exclusivity for the covered product, commercial benefits may continue to
be derived from: (i) later-granted patents on processes and intermediates
related to the most economical method of manufacture of the active ingredient
of such product; (ii) patents relating to the use of such product; (iii)
patents relating to novel compositions and formulations; and (iv) in the United
States, market exclusivity that may be available under federal law. The effect
of product patent expiration also depends upon many other factors such as the
nature of the market and the position of the product in it, the growth of the
market, the complexities and economics of the process for manufacture of the
active ingredient of the product and the requirements of new drug provisions of
the Federal Food, Drug and Cosmetic Act or similar laws and regulations in
other countries.
 
   The PTRA in the United States permits restoration of up to five years of the
patent term for new products to compensate for patent term lost during the
regulatory review process. Additionally, under the PTRA new chemical entities
approved after September 24, 1984 receive a period of five years exclusivity
from the date of NDA approval, during which time an "abbreviated NDA" or "paper
NDA" may not be submitted to the FDA. Similarly, in the case of non-new
chemical entities approved after September 24, 1984, the applications
 
                                       8
<PAGE>
 
for which include the new data of clinical investigations conducted or
sponsored by the applicant essential to approval, no abbreviated NDA or paper
NDA may become effective before three years from NDA approval. However, the
PTRA has also resulted in a general increase in the number and use of generic
products marketed in the United States because the regulatory requirements for
approval of generic versions of off-patent pioneer drugs have significantly
lessened. Additionally, the PTRA has increased the incentive for abbreviated
NDA applicants to challenge the validity of U.S. patents claiming pioneer drugs
because such a challenge could result in an earlier effective approval date for
the generic version of the pioneer drug and a six-month period during which
other generic versions of the pioneer drug could not be marketed.
 
   In 1997, the Food and Drug Administration Modernization Act was passed. The
Act includes a Pediatric Exclusivity Provision that may provide an additional
six months of market exclusivity in the United States for indications of new or
currently marketed drugs, if certain agreed upon pediatric studies are
completed by the applicant.
 
   In Japan, a patent term restoration law enacted in 1988 provides, under
specific conditions, up to five years of additional patent life for
pharmaceuticals. In 1992, the Council of the European Communities published a
regulation which created supplementary protection certificates for medicinal
products. Thus, as of January 1993, certain medicinal products sold in the EU
became eligible for up to five years of market exclusivity after patent
expiration. However, this market exclusivity will expire throughout the EU 15
years after the first product approval in the EU. In February 1993, Canada
enacted Bill C91 which significantly modified Canadian patent law by
eliminating compulsory licensing of pharmaceutical products after December 20,
1991. Thus, patented pharmaceutical products are entitled to a 20-year patent
life in Canada.
 
   The North American Free Trade Agreement was passed in November 1993.
Pursuant to the agreement, Mexico improved its patent law to meet international
standards and to provide full patent protection to pharmaceutical products. The
General Agreement on Tariffs and Trade ("GATT") negotiations were concluded in
December 1993 and the U.S. implementing legislation was enacted in December
1994. The required changes in U.S. law became effective in June 1995. The GATT
implementing law changed the patent term of new inventions to 20 years from the
date of patent filing. Existing patents were granted a patent term of the
greater of 17 years from issue or 20 years from filing. Patents on several
products of the Company obtained longer life as a result.
 
   The GATT agreement also requires countries to upgrade their intellectual
property laws to meet minimum international standards and to provide full
patent protection for pharmaceutical products not later than the end of a ten-
year transition period. Many countries have upgraded or are in the process of
upgrading their patent laws due to the GATT agreement.
 
   The Generic Animal Drug and Patent Term Restoration Act, enacted in November
1988, provides for the extension of term of patents claiming new animal drugs
approved after enactment. This legislation also establishes a process by which
generic versions of new animal drugs can be approved via an Abbreviated New
Animal Drug Application procedure. The provisions of this legislation, in
general, are parallel to those found in the PTRA covering human health
products.
 
   Worldwide, all of the Company's important products are sold under trademarks
that are considered in the aggregate to be of material importance. Trademark
protection continues in some countries as long as used; in other countries, as
long as registered. Registration is for fixed terms and can be renewed
indefinitely.
 
   Royalties received during 1998 on patent and know-how licenses and other
rights amounted to $107.6 million. The Company also paid royalties amounting to
$234.6 million in 1998 under patent and know-how licenses it holds.
 
                                       9
<PAGE>
 
Research and Development
 
   The Company's business is characterized by the introduction of new products
or new uses for existing products through a strong research and development
program. Approximately 8,500 people are employed in the Company's research
activities. Expenditures for the Company's research and development programs
were $1,821.1 million in 1998, $1,683.7 million in 1997 and $1,487.3 million in
1996 and will be approximately $2.1 billion in 1999. The Company maintains its
ongoing commitment to research over a broad range of therapeutic areas and
clinical development in support of new products. Total expenditures for the
period 1989 through 1998 exceeded $12.0 billion with a compound annual growth
rate of 11%.
 
   The Company maintains a number of long-term exploratory and fundamental
research programs in biology and chemistry as well as research programs
directed toward product development. Projects related to human and animal
health are being carried on in various fields such as bacterial and viral
infections, cardiovascular functions, cancer, diabetes, pain and inflammation,
ulcer therapy, kidney function, mental health, the nervous system, ophthalmic
research, prostate therapy, the respiratory system, bone diseases,
endoparasitic and ectoparasitic diseases, companion animal diseases and
production improvement.
 
   In the development of human and animal health products, industry practice
and government regulations in the United States and most foreign countries
provide for the determination of effectiveness and safety of new chemical
compounds through pre-clinical tests and controlled clinical evaluation. Before
a new drug may be marketed in the United States, recorded data on the
experience so gained are included in the NDA or the biological Product License
Application to the FDA for the required approval. The development of certain
other products is also subject to government regulations covering safety and
efficacy in the United States and many foreign countries. There can be no
assurance that a compound that is the result of any particular program will
obtain the regulatory approvals necessary for it to be marketed.
 
   New product candidates resulting from this research and development program
include Vioxx, a new anti-inflammatory product for the treatment of
osteoarthritis and relief of pain, for which the Company filed an NDA with the
FDA on November 23, 1998. On January 11, 1999, the FDA assigned a six-month
priority review to the Company's NDA for Vioxx. In February 1999, the Company
received confirmation that the FDA's Arthritis Advisory Committee meeting for
Vioxx has been scheduled for April 20, 1999. Other products in development
include an injectable antibiotic; an antifungal agent; an oral compound
potentially useful for treatment of chemotherapy induced emesis; an oral
compound potentially useful for the treatment of depression and other
neuropsychiatric diseases; a second COX-2 specific inhibitor potentially useful
for the treatment of osteoarthritis, rheumatoid arthritis and pain; and certain
new vaccines.
 
   All product or service marks appearing in type form different from that of
the surrounding text are trademarks or service marks owned by or licensed to
Merck & Co., Inc., its subsidiaries or affiliates. Cozaar and Hyzaar are
registered trademarks of E.I. du Pont de Nemours and Company, Wilmington, DE.
 
Employees
 
   At the end of 1998, the Company had 57,300 employees worldwide, with 35,900
employed in the United States, including Puerto Rico. Approximately 32% of the
Company's worldwide employees are represented by various collective bargaining
groups.
 
Environmental Matters
 
   The Company believes that it is in compliance in all material respects with
applicable environmental laws and regulations. In 1998, the Company incurred
capital expenditures of approximately $56.5 million for environmental
protection facilities. Capital expenditures for this purpose are forecasted to
exceed $550.0 million for the years 1999 through 2003. In addition, the
Company's operating and maintenance expenditures for environmental protection
facilities were approximately $83.4 million in 1998. Expenditures for this
purpose for the years 1999 through 2003 are forecasted to exceed $484.0
million. The Company is also
 
                                       10
<PAGE>
 
remediating environmental contamination resulting from past industrial activity
at certain of its sites. Expenditures for remediation and environmental
liabilities were $16.7 million in 1998, and are estimated at $220.0 million for
the years 1999 through 2003. These amounts do not consider potential recoveries
from insurers or other parties. The Company has taken an active role in
identifying and providing for these costs; and, therefore, management does not
believe that these expenditures should result in a materially adverse effect on
the Company's financial position, results of operations, liquidity or capital
resources.
 
Cautionary Factors that May Affect Future Results
(Cautionary Statements Under the Private Securities Litigation Reform Act of
1995)
 
   This report and other written reports and oral statements made from time to
time by the Company may contain so-called "forward-looking statements," all of
which are subject to risks and uncertainties. One can identify these forward-
looking statements by their use of words such as "expects," "plans," "will,"
"estimates," "forecasts," "projects" and other words of similar meaning. One
can also identify them by the fact that they do not relate strictly to
historical or current facts. These statements are likely to address the
Company's growth strategy, financial results, product approvals and development
programs. One must carefully consider any such statement and should understand
that many factors could cause actual results to differ from the Company's
forward-looking statements. These factors include inaccurate assumptions and a
broad variety of other risks and uncertainties, including some that are known
and some that are not. No forward-looking statement can be guaranteed and
actual future results may vary materially. Although it is not possible to
predict or identify all such factors, they may include the following:
 
  .  Generic competition as several products face expiration of product patents
     in the United States and other countries in the near term, including
     Pepcid (U.S. - 2000), Vasotec (U.S. - 2000), Mevacor (U.S. - 2001),
     Prinivil/Prinzide (U.S. - 2001) and Vaseretic (U.S. - 2001). In addition,
     Prilosec, which is supplied exclusively to Astra Pharmaceuticals, L.P.,
     will face expiration of a product patent in 2001.
 
  .  Increased "brand" competition in therapeutic areas important to the
     Company's long-term business performance.
 
  .  The difficulties and uncertainties inherent in new product development.
     The outcome of the lengthy and complex process of new product development
     is inherently uncertain. A candidate can fail at any stage of the process
     and one or more late-stage product candidates could fail to receive
     regulatory approval. New product candidates may appear promising in
     development but fail to reach the market because of efficacy or safety
     concerns, the inability to obtain necessary regulatory approvals, the
     difficulty or excessive cost to manufacture and/or the infringement of
     patents or intellectual property rights of others. Furthermore, the sales
     of new products may prove to be disappointing and fail to reach
     anticipated levels.
 
  .  Pricing pressures, both in the United States and abroad, including rules
     and practices of managed care groups, judicial decisions and governmental
     laws and regulations related to Medicare, Medicaid and healthcare reform,
     pharmaceutical reimbursement and pricing in general.
 
  .  Changes in government laws and regulations and the enforcement thereof
     affecting the Company's pharmaceutical, vaccine and/or pharmaceutical
     benefits management businesses.
 
  .  Efficacy or safety concerns with respect to marketed products, whether or
     not scientifically justified, leading to product recalls, withdrawals or
     declining sales.
 
  .  Legal factors, including product liability claims, antitrust litigation
     and investigations, environmental concerns and patent disputes with
     competitors, any of which could preclude commercialization of products or
     negatively affect the profitability of existing products.
 
  .  Lost market opportunity resulting from delays and uncertainties in the
     approval process of the FDA and foreign regulatory authorities.
 
                                       11
<PAGE>
 
  .  Changes in tax laws including changes related to the taxation of foreign
     earnings, as well as the impact of legislation capping and ultimately
     repealing Section 936 of the Internal Revenue Code (relating to earnings
     from the Company's Puerto Rican operations).
 
  .  Changes in accounting standards promulgated by the American Institute of
     Certified Public Accountants, the Financial Accounting Standards Board or
     the Securities and Exchange Commission that are adverse to the Company.
 
  .  Economic factors over which the Company has no control, including changes
     in inflation, interest rates and foreign currency exchange rates.
 
   This list should not be considered an exhaustive statement of all potential
risks and uncertainties.
 
Geographic Area and Segment Information
 
   The Company's operations outside the United States are conducted primarily
through subsidiaries. Sales of the Company's human health products by
subsidiaries outside the United States were 43% of the Company's human health
sales in 1998, and 46% and 47% in 1997 and 1996, respectively. The 1998
percentage was affected by increased domestic supply sales to Astra
Pharmaceuticals, L.P., as a result of the restructuring of AMI.
 
   The Company's worldwide business is subject to risks of currency
fluctuations, governmental actions and other governmental proceedings abroad.
The Company does not regard these risks as a deterrent to further expansion of
its operations abroad. However, the Company closely reviews its methods of
operations and adopts strategies responsive to changing economic and political
conditions.
 
   Within the EU, there has been an evolution toward a single market in
pharmaceuticals, for which Economic and Monetary Union ("EMU"), including the
adoption of the euro as a single currency, marks an important step. The Company
has recognized the strategic significance of this development and will adopt
the euro in 1999 for use in EMU markets. In this way, the Company is
demonstrating its support for the European Community's industrial policy. The
Company is continually seeking to take advantage of these opportunities to
improve the efficiency and productivity of its EU operations.
 
   In recent years, the Company has been expanding its operations in countries
located in Latin America, the Middle East, Africa, Eastern Europe and Asia
Pacific where changes in government policies and economic conditions are making
it possible for the Company to earn fair returns. Business in these developing
areas, while sometimes less stable, offers important opportunities for growth
over time.
 
   Financial information about geographic areas and operating segments of the
Company's business is incorporated by reference to page 51 of the Company's
1998 Annual Report to stockholders.
 
Other Matters
 
   The Company has developed and begun implementing a plan to ensure that its
systems are compliant with the requirements to process transactions in the year
2000. The continued efficient operation of the Company's business will be
dependent upon the ability of its systems to process date sensitive information
in the Year 2000. As a result, the Company initiated a program in 1996 to
inventory all critical systems, assess the impact of Year 2000 noncompliance,
develop plans to remediate or replace noncompliant systems and assess the
readiness of key third parties. The inventory and assessment phases are
complete for internal information technology ("IT") systems and the Company is
approximately 75% complete with the remediation phase as of December 31, 1998.
The evaluation and remediation phases for non-IT systems (e.g. building,
process and factory control systems) are currently underway. Although the
Company has designed these programs to properly prepare its systems for the
Year 2000, there can be no assurance that the Company will not experience
 
                                       12
<PAGE>
 
business disruptions or incur material costs caused by the failure to detect
and remediate all instances of Year 2000 noncompliance in its systems. Failure
to complete these programs as planned could result in the corruption of data,
hardware or equipment failures or the inability to manufacture products or
conduct other business activities, all of which could have a material impact on
the Company's business, results of operations or financial position.
Contingency plans (including the substitution of systems, use of manual methods
and other means to prevent the failure of critical systems from having a
material effect on the Company) are under development, particularly for high
risk areas such as those involving supplier and product management.
 
   In addition to risks associated with internal systems, the Company has
relationships with, and is to varying degrees dependent upon, third parties
that provide the Company with information, goods and services. These include
financial institutions, suppliers, utilities, vendors, research partners and
governmental entities, as well as customers and distributors. If a significant
number of these third parties experience failures in their systems due to Year
2000 noncompliance, it could affect the Company's ability to process
transactions, manufacture products or engage in other business activities.
While some of these risks are outside of the Company's control, the Company has
instituted programs, including internal records review and external
questionnaires and supplier audits, to identify key third parties, assess their
level of Year 2000 compliance, update contracts, develop supplier-based
contingency plans and address any noncompliance issues.
 
   All critical aspects of the Company's Year 2000 compliance program are
expected to be completed by the end of the third quarter 1999. Total costs to
resolve the Year 2000 issue are not expected to be material to the Company's
financial position, results of operations or cash flows.
 
Item 2. Properties.
 
   The Company's corporate headquarters is located in Whitehouse Station, New
Jersey. The Company's pharmaceutical business is conducted through divisional
headquarters located in Rahway, New Jersey and West Point, Pennsylvania.
Principal research facilities for human and animal health products are located
in Rahway and West Point. The Company also has production facilities for human
and animal health products at nine locations in the United States and Puerto
Rico. Branch warehouses provide services throughout the country. Outside the
United States, through subsidiaries, the Company owns or has an interest in
manufacturing plants or other properties in Australia, Canada, countries in
Western Europe, Central and South America, Africa and Asia. Merck-Medco
operates its primary businesses through its headquarters located in Montvale,
New Jersey, and through owned or leased facilities in various locations
throughout the United States.
 
   Capital expenditures for 1998 were $1,973.4 million compared with $1,448.8
million for 1997. In the United States, these amounted to $1,413.6 million for
1998 and $1,062.8 million for 1997. Abroad, such expenditures amounted to
$559.8 million for 1998 and $386.0 million for 1997.
 
   The Company and its subsidiaries own their principal facilities and
manufacturing plants under titles which they consider to be satisfactory. The
Company considers that its properties are in good operating condition and that
its machinery and equipment have been well maintained. Plants for the
manufacture of products are suitable for their intended purposes and have
capacities and projected capacities adequate for current and projected needs
for existing Company products. Some capacity of the plants is being converted,
with any needed modification, to the requirements of newly introduced and
future products.
 
Item 3. Legal Proceedings.
 
   The Company, including Merck-Medco, is party to a number of antitrust suits,
certain of which have been certified as class actions, instituted by most of
the nation's retail pharmacies and consumers in several states, alleging
conspiracies in restraint of trade and challenging the pricing and/or
purchasing practices of the Company and Merck-Medco, respectively. A
significant number of other pharmaceutical companies and wholesalers have also
been sued in the same or similar litigation. These actions, except for several
actions pending in state courts, have been consolidated for pre-trial purposes
in the United States District Court for the
 
                                       13
<PAGE>
 
Northern District of Illinois. In 1996, the Company and several other
defendants finalized an agreement to settle the federal class action alleging
conspiracy, which represents the single largest group of retail pharmacy
claims, pursuant to which the Company paid $51.8 million. Since that time, the
Company has entered into other settlements on satisfactory terms. The Company
has not engaged in any conspiracy and no admission of wrongdoing was made nor
was included in the final agreements. While it is not feasible to predict the
final outcome of these proceedings, in the opinion of the Company, such
proceedings should not ultimately result in any liability which would have a
materially adverse effect on the financial position, liquidity or results of
operations of the Company.
 
   The Company is a party to a number of proceedings brought under the
Comprehensive Environmental Response, Compensation and Liability Act, commonly
known as Superfund. These proceedings seek to require the operators of
hazardous waste disposal facilities, transporters of waste to the sites and
generators of hazardous waste disposed of at the sites to clean up the sites or
to reimburse the government for cleanup costs. The Company has been made a
party to these proceedings as an alleged generator of waste disposed of at the
sites. In each case, the government alleges that the defendants are jointly and
severally liable for the cleanup costs. Although joint and several liability is
alleged, these proceedings are frequently resolved so that the allocation of
cleanup costs among the parties more nearly reflects the relative contributions
of the parties to the site situation. The Company's potential liability varies
greatly from site to site. For some sites the potential liability is de minimis
and for others the costs of cleanup have not yet been determined. While it is
not feasible to predict the outcome of many of these proceedings brought by
federal or state agencies or private litigants, in the opinion of the Company,
such proceedings should not ultimately result in any liability which would have
a materially adverse effect on the financial position, results of operations,
liquidity or capital resources of the Company. The Company has taken an active
role in identifying and providing for these costs and such amounts do not
include any reduction for anticipated recoveries of cleanup costs from
insurers, former site owners or operators or other recalcitrant potentially
responsible parties.
 
   In November 1994, the Company, along with other pharmaceutical manufacturers
and pharmaceutical benefits managers ("PBMs"), received a notice from the
Federal Trade Commission ("FTC") that the FTC intended to investigate
agreements, alliances, activities and acquisitions involving pharmaceutical
manufacturers and PBMs. In August 1998, the Company and Merck-Medco reached an
agreement with the FTC that resolves the investigation as to the Company and
Merck-Medco. The agreement formalizes the policies and practices the Company
and Merck-Medco voluntarily adopted over four years ago governing the operation
of their businesses. The agreement will not affect how the Company and Merck-
Medco currently compete in the marketplace, serve their customers or conduct
business with third parties. Accordingly, the Company does not believe that the
agreement will have a materially adverse effect on the Company's financial
position, liquidity or results of operations.
 
   In March 1996, the Company, along with other pharmaceutical manufacturers,
received a notice from the FTC that it was conducting an investigation into
pricing practices. The Company has cooperated fully with the FTC in this
investigation, and believes that it is currently operating in all material
respects in accordance with applicable standards. Accordingly, although the
Company cannot predict the outcome of this investigation, it does not believe
it will have a materially adverse effect on the financial position, liquidity
or results of operations of the Company.
 
   There are various other legal proceedings, principally product liability and
intellectual property suits involving the Company, which are pending. While it
is not feasible to predict the outcome of these proceedings, in the opinion of
the Company, all such proceedings are either adequately covered by insurance
or, if not so covered, should not ultimately result in any liability which
would have a materially adverse effect on the financial position, liquidity or
results of operations of the Company.
 
Item 4. Submission of Matters to a Vote of Security Holders.
 
   Not applicable.
 
                                       14
<PAGE>
 
Executive Officers of the Registrant (as of March 1, 1999)
 
RAYMOND V. GILMARTIN -- Age 57
 
   November, 1994 -- Chairman of the Board, President and Chief Executive
   Officer
 
   June, 1994 -- President and Chief Executive Officer
 
   Prior to June, 1994, Mr. Gilmartin was Chairman, President and Chief
   Executive Officer (1992 to 1994) of Becton Dickinson and Company (medical
   supplies and devices and diagnostic systems).
 
DAVID W. ANSTICE -- Age 50
 
   January, 1997 -- President, Human Health-The Americas -- responsible for the
   Company's prescription drug business in the United States, Canada and Latin
   America and medical and scientific affairs
 
   September, 1994 -- President, Human Health-U.S./Canada -- responsible for
   the Company's prescription drug business in the United States and Canada,
   worldwide coordination of marketing policies and medical and scientific
   affairs
 
   January, 1994 -- President, Human Health Europe
 
PAUL R. BELL -- Age 53
 
   April, 1997 -- President, Human Health-Asia Pacific -- responsible for the
   Company's prescription drug business in the Far East, Australia, New Zealand
   and Japan
 
   March, 1994 -- Vice President and Managing Director -- Australia and New
   Zealand
 
CELIA A. COLBERT -- Age 42
 
   January, 1997 -- Vice President, Secretary and Assistant General Counsel
 
   November, 1993 -- Secretary and Assistant General Counsel
 
LINDA M. DISTLERATH -- Age 45
 
   January, 1999 -- Vice President, Public Affairs -- responsible for public
   affairs and The Merck Company Foundation (a not-for-profit charitable
   organization affiliated with the Company)
 
   October, 1997 -- Executive Director, Public Policy and Merck Research
   Laboratories (MRL) Public Affairs
 
   April, 1995 -- Executive Director, MRL Public Affairs
 
   October, 1990 -- Senior Director, Science & Technology Policy -- responsible
   for public policy strategies in support of the Company's research and
   development programs
 
CAROLINE DORSA -- Age 39
 
   February, 1999 -- Vice President and Treasurer -- responsible for the
   Company's treasury and tax functions
 
   January, 1997 -- Vice President and Treasurer
 
   January, 1994 -- Treasurer
 
R. GORDON DOUGLAS JR. -- Age 64
 
   April, 1991 -- President, Merck Vaccines
 
KENNETH C. FRAZIER -- Age 44
 
   January, 1999 -- Vice President and Deputy General Counsel
 
   January, 1997 -- Vice President, Public Affairs and Assistant General
   Counsel -- responsible for public affairs, corporate legal activities and
   The Merck Company Foundation (a not-for-profit charitable organization
   affiliated with the Company)
 
                                       15
<PAGE>
 
   April, 1994 -- Vice President, Public Affairs
 
   May, 1992 -- Vice President, General Counsel and Secretary, Astra/Merck
   Group (a joint venture affiliated with the Company)
 
RICHARD C. HENRIQUES JR. -- Age 43
 
   February, 1999 -- Vice President, Controller -- responsible for the
   Corporate Controller's Group and providing financial support for U.S. Human
   Health, Canada and Latin America (The Americas)
 
   January, 1998 -- Vice President & Controller, The Americas
 
   January, 1997 -- Controller, The Americas
 
   January, 1994 -- Controller, North America Pharmaceutical Care
 
BERNARD J. KELLEY -- Age 57
 
   December, 1993 -- President, Merck Manufacturing Division
 
JUDY C. LEWENT -- Age 50
 
   January, 1997 -- Senior Vice President and Chief Financial Officer --
    responsible for financial and corporate development functions, internal
   auditing and the Company's joint venture relationships
 
   September, 1994 -- Senior Vice President and Chief Financial Officer --
    responsible for financial and public affairs functions, The Merck Company
   Foundation (a not-for-profit charitable organization affiliated with the
   Company), internal auditing and the Company's joint venture relationships
 
   December, 1993 -- Senior Vice President and Chief Financial Officer (since
   January 1993) -- responsible for financial and public affairs functions and
   The Merck Company Foundation
 
PER G. H. LOFBERG -- Age 51
 
   December, 1995 -- President, Merck-Medco Managed Care, L.L.C., a wholly-
   owned subsidiary of the Company
 
   January, 1994 -- President, Merck-Medco Managed Care Division
 
MARY M. MCDONALD -- Age 54
 
   January, 1999 -- Senior Vice President and General Counsel -- responsible
   for legal, public affairs and human resources functions and The Merck
   Company Foundation (a not-for-profit charitable organization affiliated with
   the Company)
 
   January, 1997 -- Senior Vice President and General Counsel -- responsible
   for legal and public affairs functions and The Merck Company Foundation
 
   January, 1993 -- Senior Vice President and General Counsel
 
PETER E. NUGENT -- Age 56
 
   Vice President, retiring effective May 1, 1999
 
   September, 1993 to February, 1999 -- Vice President, Controller
 
EDWARD M. SCOLNICK -- Age 58
 
   September, 1994 -- Executive Vice President, Science and Technology and
   President, Merck Research Laboratories (MRL) -- responsible for worldwide
   research function and activities of Merck Manufacturing Division (MMD),
   computer resources and corporate licensing
 
                                       16
<PAGE>
 
   December, 1993 -- Executive Vice President, Science and Technology and
   President, MRL -- responsible for worldwide research function and activities
   of MMD and computer resources
 
BENNETT M. SHAPIRO -- Age 59
 
   September, 1990 -- Executive Vice President, Worldwide Basic Research, Merck
   Research Laboratories
 
PER WOLD-OLSEN -- Age 51
 
   January, 1997 -- President, Human Health-Europe, Middle East & Africa --
    responsible for the Company's prescription drug business in Europe, the
   Middle East and Africa and worldwide coordination of marketing policies
 
   September, 1994 -- President, Human Health-Europe -- responsible for the
   Company's European prescription drug business
 
   January, 1994 -- Senior Vice President, Worldwide Human Health Marketing
 
   All officers listed above serve at the pleasure of the Board of Directors.
None of these officers, other than Mr. Gilmartin (who has an employment
agreement with the Company which is an exhibit to this Form 10-K) was elected
pursuant to any arrangement or understanding between the officer and the Board.
There are no family relationships among the officers listed above.
 
                                    PART II
 
Item 5. Market for Registrant's Common Equity and Related Stockholder Matters.
 
   The information required for this item is incorporated by reference to pages
39 and 54 of the Company's 1998 Annual Report to stockholders.
 
Item 6. Selected Financial Data.
 
   The information required for this item is incorporated by reference to the
data for the last five fiscal years of the Company included under Results for
Year and Year-End Position in the Selected Financial Data table on page 54 of
the Company's 1998 Annual Report to stockholders.
 
Item 7. Management's Discussion and Analysis of Financial Condition and Results
of Operations.
 
   The information required for this item is incorporated by reference to pages
30 through 39 of the Company's 1998 Annual Report to stockholders.
 
Item 7A. Quantitative and Qualitative Disclosures About Market Risk.
 
   The information required for this item is incorporated by reference to pages
37 (under the caption "Analysis of Liquidity and Capital Resources") to 39 of
the Company's 1998 Annual Report to stockholders.
 
Item 8. Financial Statements and Supplementary Data.
 
   (a) Financial Statements
 
   The consolidated balance sheet of Merck & Co., Inc. and subsidiaries as of
December 31, 1998 and 1997, and the related consolidated statements of income,
retained earnings, comprehensive income and cash flows for each of the three
years in the period ended December 31, 1998 and the report dated January 26,
1999 of Arthur Andersen LLP, independent public accountants, are incorporated
by reference to pages 40 through 51 and page 52 of the Company's 1998 Annual
Report to stockholders.
 
                                       17
<PAGE>
 
   (b) Supplementary Data
 
   Selected quarterly financial data for 1998 and 1997 are incorporated by
reference to the data contained in the Condensed Interim Financial Data table
on page 39 of the Company's 1998 Annual Report to stockholders.
 
Item 9. Changes in and Disagreements with Accountants on Accounting and
Financial Disclosure.
 
   Not applicable.
 
                                   PART III
 
Item 10. Directors and Executive Officers of the Registrant.
 
   The required information on directors and nominees is incorporated by
reference to pages 2 (beginning with the caption "Election of Directors") to 6
of the Company's Proxy Statement for the Annual Meeting of Stockholders to be
held April 27, 1999. Information on executive officers is set forth in Part I
of this document on pages 15 through 17. The required information on
compliance with Section 16(a) of the Securities Exchange Act of 1934 is
incorporated by reference to page 23 (under the caption "Section 16(a)
Beneficial Ownership Reporting Compliance") of the Company's Proxy Statement
for the Annual Meeting of Stockholders to be held April 27, 1999.
 
Item 11. Executive Compensation.
 
   The information required for this item is incorporated by reference to
pages 7 (under the caption "Compensation of Directors") and 8, and 9
(beginning with the caption "Compensation and Benefits Committee Report on
Executive Compensation") to 19 of the Company's Proxy Statement for the Annual
Meeting of Stockholders to be held April 27, 1999.
 
Item 12. Security Ownership of Certain Beneficial Owners and Management.
 
   The information required for this item is incorporated by reference to
pages 8 (under the caption "Security Ownership of Directors and Executive
Officers") and 9 of the Company's Proxy Statement for the Annual Meeting of
Stockholders to be held April 27, 1999.
 
Item 13. Certain Relationships and Related Transactions.
 
   Not applicable.
 
                                    PART IV
 
Item 14. Exhibits, Financial Statement Schedules, and Reports on Form 8-K.
 
   (a) Documents filed as part of this Form 10-K
 
   1. Financial Statements
 
     The following consolidated financial statements and report of
  independent public accountants are incorporated herein by reference to the
  Company's 1998 Annual Report to stockholders, as noted on page 18 of this
  document:
 
     Consolidated statement of income for the years ended December 31, 1998,
  1997 and 1996
 
     Consolidated statement of retained earnings for the years ended December
  31, 1998, 1997 and 1996
 
                                      18
<PAGE>
 
     Consolidated statement of comprehensive income for the years ended
  December 31, 1998, 1997 and 1996
 
     Consolidated balance sheet as of December 31, 1998 and 1997
 
     Consolidated statement of cash flows for the years ended December 31,
  1998, 1997 and 1996
 
     Notes to consolidated financial statements
 
     Report of independent public accountants
 
2. Financial Statement Schedules
 
     Schedules are omitted because they are either not required or not
  applicable.
 
   The registrant is primarily an operating company and all of the subsidiaries
included in the consolidated financial statements filed are wholly owned except
for minority interests in five consolidated subsidiaries.
 
 
                                       19
<PAGE>
 
3. Exhibits
 
<TABLE>
<CAPTION>
 Exhibit
 Number      Description                             Method of Filing
 -------     -----------                             ----------------
 <C>     <C> <S>                                     <C>
   2.1   --  Master Restructuring Agreement dated    ***
              as of June 19, 1998
              between Astra AB, Merck & Co., Inc.,
              Astra Merck Inc.,
              Astra USA, Inc., KB USA, L.P., Astra
              Merck Enterprises, Inc.,
              KBI Sub Inc., Merck Holdings, Inc.
              and Astra Pharmaceuticals,
              L.P. (Portions of this Exhibit are
              subject to a request for
              confidential treatment filed with
              the Commission)
 
   3(a)  --  Restated Certificate of Incorporation   Incorporated by reference
              of Merck & Co., Inc.                    to Form 10-K Annual
              (May 6, 1992)                           Report for the fiscal
                                                      year ended December 31,
                                                      1992
 
   3(b)  --  Certificate of Amendment to the         Filed with this document
              Certificate of Incorporation of
              Merck & Co., Inc. (as amended January
              14, 1999, effective
              February 16, 1999)
 
   3(c)  --  By-Laws of Merck & Co., Inc. (as        Incorporated by reference
              amended effective                       to Form 10-Q Quarterly
              February 25, 1997)                      Report for the period
                                                      ended March 31, 1997
 
  10(a)  --  Executive Incentive Plan (as amended    **
              effective February 27, 1996)
 
  10(b)  --  Base Salary Deferral Plan (as adopted   Incorporated by reference
              on October 22, 1996,                    to Form 10-K Annual
              effective January 1, 1997)              Report for the fiscal year
                                                      ended December 31, 1996
 
  10(c)  --  1987 Incentive Stock Plan (as amended   Incorporated by reference
              effective May 6, 1992)                  to Form 10-K Annual
                                                      Report for the fiscal year
                                                      ended December 31, 1992
 
  10(d)  --  1991 Incentive Stock Plan (as amended   *
              effective February 23, 1994)
 
  10(e)  --  1996 Incentive Stock Plan (as amended   **
              on October 24, 1995,
              effective January 1, 1996)
 
  10(f)  --  Non-Employee Directors Stock Option     Incorporated by reference
              Plan (as amended and                    to Form 10-K Annual
              restated February 24, 1998)             Report for the fiscal year
                                                      ended December 31, 1997
 
  10(g)  --  1996 Non-Employee Directors Stock       Incorporated by reference
              Option Plan (as amended                 to Form 10-K Annual
              and restated February 24, 1998)         Report for the fiscal
                                                      year ended December 31,
                                                      1997
</TABLE>
 
                                       20
<PAGE>
 
<TABLE>
<CAPTION>
 Exhibit
 Number      Description                              Method of Filing
 -------     -----------                              ----------------
 <C>     <C> <S>                                      <C>
  10(h)  --  Supplemental Retirement Plan (as         *
              amended effective January 1, 1995)
 
  10(i)  --  Retirement Plan for the Directors of     Incorporated by reference
              Merck & Co., Inc. (amended and           to Form 10-Q Quarterly
              restated June 21, 1996)                  Report for the period
                                                       ended June 30, 1996
 
  10(j)  --  Plan for Deferred Payment of             Incorporated by reference
              Directors' Compensation (amended and     to Form 10-Q Quarterly
              restated June 21, 1996)                  Report for the period
                                                       ended June 30, 1996
 
  10(k)  --  Form of Stock Option Agreement dated     ****
              October 14, 1992 between Merck-Medco
              and Per G.H. Lofberg (together with a
              list showing the number of options
              held)
 
  10(l)  --  Employment Agreement between Per G.H.    Incorporated by reference
              Lofberg and Merck-Medco dated April      to Form 10-K Annual
              1, 1993                                  Report of Medco
                                                       Containment Services,
                                                       Inc. for the fiscal year
                                                       ended June 30, 1993
 
  10(m)  --  Amendment dated July 27, 1993 to         **
              Employment Agreement between Per G.H.
              Lofberg and Merck-Medco dated April
              1, 1993
 
  10(n)  --  Letter Agreement dated May 24, 1996      Incorporated by reference
              with respect to the Employment           to Form 10-Q Quarterly
              Agreement between Per G.H. Lofberg       Report for the period
              and Merck-Medco dated April 1, 1993      ended June 30, 1996
              and amended July 27, 1993
 
  10(o)  --  Employment Agreement between Raymond     Incorporated by reference
              V. Gilmartin and the Company dated       to Form 10-Q Quarterly
              June 9, 1994                             Report for the period
                                                       ended June 30, 1994
 
  10(p)  --  Amended and Restated License and         ***
              Option Agreement dated as of July 1,
              1998 between Astra AB and Astra Merck
              Inc.
 
  10(q)  --  KBI Shares Option Agreement dated as     ***
              of July 1, 1998 by and among Astra
              AB, Merck & Co., Inc. and Merck
              Holdings, Inc.
 
  10(r)  --  KBI-E Asset Option Agreement dated as    ***
              of July 1, 1998 by and among Astra
              AB, Merck & Co., Inc., Astra Merck
              Inc. and Astra Merck Enterprises Inc.
 
  10(s)  --  KBI Supply Agreement dated as of July    ***
              1, 1998 between Astra Merck Inc. and
              Astra Pharmaceuticals, L.P. (Portions
              of this Exhibit are subject to a
              request for confidential treatment
              filed with the Commission)
 
  10(t)  --  Second Amended and Restated              ***
              Manufacturing Agreement dated as of
              July 1, 1998 among Merck & Co., Inc.,
              Astra AB, Astra Merck Inc. and Astra
              USA, Inc.
 
  10(u)  --  Limited Partnership Agreement dated as   ***
              of July 1, 1998 between KB USA, L.P.
              and KBI Sub Inc.
 
</TABLE>
 
 
 
                                       21
<PAGE>
 
<TABLE>
<CAPTION>
 Exhibit
 Number      Description                               Method of Filing
 -------     -----------                               ----------------
 <C>     <C> <S>                                       <C>
  10(v)  --  Distribution Agreement dated as of July   ***
              1, 1998 between Astra Merck
              Enterprises Inc. and Astra
              Pharmaceuticals, L.P.
 
  10(w)  --  Agreement to Incorporate Defined Terms    ***
              dated as of June 19, 1998 between
              Astra AB, Merck & Co., Inc., Astra
              Merck Inc., Astra USA, Inc., KB USA,
              L.P., Astra Merck Enterprises Inc.,
              KBI Sub Inc., Merck Holdings, Inc. and
              Astra Pharmaceuticals, L.P.
 
  12     --  Computation of Ratios of Earnings to      Filed with this document
              Fixed Charges
 
  13     --  1998 Annual Report to stockholders        Filed with this document
              (only those portions incorporated by
              reference in this document are deemed
              "filed")
 
  21     --  List of subsidiaries                      Filed with this document
 
  23     --  Consent of Independent Public             Contained on page 24
              Accountants                               of this Report
 
  24     --  Power of Attorney and Certified           Filed with this document
              Resolution of Board of Directors
 
  27(a)  --  Financial Data Schedule                   Filed with this document
 
  27(b)  --  Restated Financial Data Schedule          Filed with this document
 
  27(c)  --  Restated Financial Data Schedule          Filed with this document
</TABLE>
- --------
*   Incorporated by reference to Form 10-K Annual Report for the fiscal year
    ended December 31, 1994
**  Incorporated by reference to Form 10-K Annual Report for the fiscal year
    ended December 31, 1995
*** Incorporated by reference to Form 10-Q Quarterly Report for the period
    ended June 30, 1998
****  Incorporated by reference to Post Effective Amendment No. 1 to
      Registration Statement on Form S-8 to Form S-4 Registration Statement
      (No. 33-50667)
 
   None of the instruments defining the rights of holders of long-term debt of
the Company and its subsidiaries (Exhibit Number 4) are being filed since the
total amount of securities authorized under any of such instruments taken
individually does not exceed 10% of the total assets of the Company and its
subsidiaries on a consolidated basis. The Company agrees to furnish a copy of
such instruments to the Commission upon request.
 
   Copies of the exhibits may be obtained by stockholders upon written request
directed to the Stockholder Services Department, Merck & Co., Inc., P.O. Box
100 -- WS 3AB-40, Whitehouse Station, New Jersey 08889-0100 accompanied by
check in the amount of $5.00 payable to Merck & Co., Inc. to cover processing
and mailing costs.
 
   (b) Reports on Form 8-K
 
   During the three-month period ended December 31, 1998, one Current Report
was filed on Form 8-K under Item 5 --  Other Events regarding the Company's
business briefing to analysts. This report was dated and filed December 9,
1998.
 
                                       22
<PAGE>
 
                                   SIGNATURES
 
   Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, the registrant has duly caused this report to be signed
on its behalf by the undersigned, thereunto duly authorized.
 
                                          MERCK & CO., INC.
 
                                                           /s/
Dated: March 23, 1999                     By: _________________________________
                                                   Raymond V. Gilmartin
                                             (Chairman of the Board, President
                                               and Chief Executive Officer)
 
                                                     /s/ Celia A. Colbert
                                              By: _____________________________
                                                       Celia A. Colbert
                                                      (Attorney-in-Fact)
 
   Pursuant to the requirements of the Securities Exchange Act of 1934, this
report has been signed below by the following persons on behalf of the
registrant and in the capacities and on the dates indicated.
 
<TABLE>
<CAPTION>
            Signatures                         Title                       Date
            ----------                         -----                       ----
<S>                                <C>                           <C>
              /s/                  Chairman of the Board,             March 23, 1999
_________________________________   President and Chief
      Raymond V. Gilmartin          Executive Officer;
                                    Principal Executive
                                    Officer; Director

              /s/                  Senior Vice President and          March 23, 1999
_________________________________   Chief Financial Officer;
         Judy C. Lewent             Principal Financial Officer

              /s/                  Vice President, Controller;        March 23, 1999
_________________________________   Principal Accounting
    Richard C. Henriques Jr.        Officer

              /s/                  Director                           March 23, 1999
_________________________________
    H. Brewster Atwater, Jr.

              /s/                  Director                           March 23, 1999
_________________________________
          Derek Birkin

              /s/                  Director                           March 23, 1999
_________________________________
       Lawrence A. Bossidy

              /s/                  Director                           March 23, 1999
_________________________________
        William G. Bowen

              /s/                  Director                           March 23, 1999
_________________________________
        Johnnetta B. Cole

              /s/                  Director                           March 23, 1999
_________________________________
        Carolyne K. Davis

              /s/                  Director                           March 23, 1999
_________________________________
          Lloyd C. Elam

              /s/                  Director                           March 23, 1999
_________________________________
      Charles E. Exley, Jr.

              /s/                  Director                           March 23, 1999
_________________________________
        William N. Kelley

              /s/                  Director                           March 23, 1999
_________________________________
       Edward M. Scolnick

              /s/                  Director                           March 23, 1999
_________________________________
         Samuel O. Thier

              /s/                  Director                           March 23, 1999
_________________________________
       Dennis Weatherstone
</TABLE>
 
   Celia A. Colbert, by signing her name hereto, does hereby sign this document
pursuant to powers of attorney duly executed by the persons named, filed with
the Securities and Exchange Commission as an exhibit to this document, on
behalf of such persons, all in the capacities and on the date stated, such
persons including all of the directors of the Company.
 
                                                     /s/ Celia A. Colbert
                                              By: _____________________________
                                                       Celia A. Colbert
                                                      (Attorney-in-Fact)
 

 
                                       23
<PAGE>
 
 
                                                                      Exhibit 23
                                                                                


                   CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS
                                        

    As independent public accountants, we hereby consent to the incorporation by
reference in this Form 10-K of our report dated January 26, 1999 included in the
Company's Annual Report to stockholders for the fiscal year ended December 31,
1998, into the Company's previously filed Registration Statements on Form S-8
(Nos. 33-21087, 33-21088, 33-36101, 33-40177, 33-51235, 33-53463, 33-64273, 33-
64665, 333-23293 and 333-23295), on Form S-4 (No. 33-50667) and on Form S-3
(Nos. 33-39349, 33-60322, 33-51785, 33-57421, 333-17045 and 333-36383).  It
should be noted that we have not audited any financial statements of the Company
subsequent to December 31, 1998 or performed any audit procedures subsequent to
the date of our report.



                                                    ARTHUR ANDERSEN LLP

New York, New York
March 23, 1999



                                      24
<PAGE>
 
                                 EXHIBIT INDEX
 
<TABLE>
<CAPTION>
 Exhibit
 Number      Description                             Method of Filing
 -------     -----------                             ----------------
 <C>     <C> <S>                                     <C>
   2.1   --  Master Restructuring Agreement dated    ***
              as of June 19, 1998
              between Astra AB, Merck & Co., Inc.,
              Astra Merck Inc.,
              Astra USA, Inc., KB USA, L.P., Astra
              Merck Enterprises, Inc.,
              KBI Sub Inc., Merck Holdings, Inc.
              and Astra Pharmaceuticals,
              L.P. (Portions of this Exhibit are
              subject to a request for
              confidential treatment filed with
              the Commission)
 
   3(a)  --  Restated Certificate of Incorporation   Incorporated by reference
              of Merck & Co., Inc.                    to Form 10-K Annual
              (May 6, 1992)                           Report for the fiscal
                                                      year ended December 31,
                                                      1992
 
   3(b)  --  Certificate of Amendment to the         Filed with this document
              Certificate of Incorporation of
              Merck & Co., Inc. (as amended January
              14, 1999, effective
              February 16, 1999)
 
   3(c)  --  By-Laws of Merck & Co., Inc. (as        Incorporated by reference
              amended effective                       to Form 10-Q Quarterly
              February 25, 1997)                      Report for the period
                                                      ended March 31, 1997
 
  10(a)  --  Executive Incentive Plan (as amended    **
              effective February 27, 1996)
 
  10(b)  --  Base Salary Deferral Plan (as adopted   Incorporated by reference
              on October 22, 1996,                    to Form 10-K Annual
              effective January 1, 1997)              Report for the fiscal year
                                                      ended December 31, 1996
 
  10(c)  --  1987 Incentive Stock Plan (as amended   Incorporated by reference
              effective May 6, 1992)                  to Form 10-K Annual
                                                      Report for the fiscal year
                                                      ended December 31, 1992
 
  10(d)  --  1991 Incentive Stock Plan (as amended   *
              effective February 23, 1994)
 
  10(e)  --  1996 Incentive Stock Plan (as amended   **
              on October 24, 1995,
              effective January 1, 1996)
 
  10(f)  --  Non-Employee Directors Stock Option     Incorporated by reference
              Plan (as amended and                    to Form 10-K Annual
              restated February 24, 1998)             Report for the fiscal year
                                                      ended December 31, 1997
 
  10(g)  --  1996 Non-Employee Directors Stock       Incorporated by reference
              Option Plan (as amended                 to Form 10-K Annual
              and restated February 24, 1998)         Report for the fiscal
                                                      year ended December 31,
                                                      1997
</TABLE>
<PAGE>
 
<TABLE>
<CAPTION>
 Exhibit
 Number      Description                              Method of Filing
 -------     -----------                              ----------------
 <C>     <C> <S>                                      <C>
  10(h)  --  Supplemental Retirement Plan (as         *
              amended effective January 1, 1995)
 
  10(i)  --  Retirement Plan for the Directors of     Incorporated by reference
              Merck & Co., Inc. (amended and           to Form 10-Q Quarterly
              restated June 21, 1996)                  Report for the period
                                                       ended June 30, 1996
 
  10(j)  --  Plan for Deferred Payment of             Incorporated by reference
              Directors' Compensation (amended and     to Form 10-Q Quarterly
              restated June 21, 1996)                  Report for the period
                                                       ended June 30, 1996
 
  10(k)  --  Form of Stock Option Agreement dated     ****
              October 14, 1992 between Merck-Medco
              and Per G.H. Lofberg (together with a
              list showing the number of options
              held)
 
  10(l)  --  Employment Agreement between Per G.H.    Incorporated by reference
              Lofberg and Merck-Medco dated April      to Form 10-K Annual
              1, 1993                                  Report of Medco
                                                       Containment Services,
                                                       Inc. for the fiscal year
                                                       ended June 30, 1993
 
  10(m)  --  Amendment dated July 27, 1993 to         **
              Employment Agreement between Per G.H.
              Lofberg and Merck-Medco dated April
              1, 1993
 
  10(n)  --  Letter Agreement dated May 24, 1996      Incorporated by reference
              with respect to the Employment           to Form 10-Q Quarterly
              Agreement between Per G.H. Lofberg       Report for the period
              and Merck-Medco dated April 1, 1993      ended June 30, 1996
              and amended July 27, 1993
 
  10(o)  --  Employment Agreement between Raymond     Incorporated by reference
              V. Gilmartin and the Company dated       to Form 10-Q Quarterly
              June 9, 1994                             Report for the period
                                                       ended June 30, 1994
 
  10(p)  --  Amended and Restated License and         ***
              Option Agreement dated as of July 1,
              1998 between Astra AB and Astra Merck
              Inc.
 
  10(q)  --  KBI Shares Option Agreement dated as     ***
              of July 1, 1998 by and among Astra
              AB, Merck & Co., Inc. and Merck
              Holdings, Inc.
 
  10(r)  --  KBI-E Asset Option Agreement dated as    ***
              of July 1, 1998 by and among Astra
              AB, Merck & Co., Inc., Astra Merck
              Inc. and Astra Merck Enterprises Inc.
 
  10(s)  --  KBI Supply Agreement dated as of July    ***
              1, 1998 between Astra Merck Inc. and
              Astra Pharmaceuticals, L.P. (Portions
              of this Exhibit are subject to a
              request for confidential treatment
              filed with the Commission)
 
  10(t)  --  Second Amended and Restated              ***
              Manufacturing Agreement dated as of
              July 1, 1998 among Merck & Co., Inc.,
              Astra AB, Astra Merck Inc. and Astra
              USA, Inc.
 
  10(u)  --  Limited Partnership Agreement dated as   ***
              of July 1, 1998 between KB USA, L.P.
              and KBI Sub Inc.
 
</TABLE>
 
 
<PAGE>
 
<TABLE>
<CAPTION>
 Exhibit
 Number      Description                               Method of Filing
 -------     -----------                               ----------------
 <C>     <C> <S>                                       <C>
  10(v)  --  Distribution Agreement dated as of July   ***
              1, 1998 between Astra Merck
              Enterprises Inc. and Astra
              Pharmaceuticals, L.P.
 
  10(w)  --  Agreement to Incorporate Defined Terms    ***
              dated as of June 19, 1998 between
              Astra AB, Merck & Co., Inc., Astra
              Merck Inc., Astra USA, Inc., KB USA,
              L.P., Astra Merck Enterprises Inc.,
              KBI Sub Inc., Merck Holdings, Inc. and
              Astra Pharmaceuticals, L.P.
 
  12     --  Computation of Ratios of Earnings to      Filed with this document
              Fixed Charges
 
  13     --  1998 Annual Report to stockholders        Filed with this document
              (only those portions incorporated by
              reference in this document are deemed
              "filed")
 
  21     --  List of subsidiaries                      Filed with this document
 
  23     --  Consent of Independent Public             Contained on page 24
              Accountants                               of this Report
 
  24     --  Power of Attorney and Certified           Filed with this document
              Resolution of Board of Directors
 
  27(a)  --  Financial Data Schedule                   Filed with this document
 
  27(b)  --  Restated Financial Data Schedule          Filed with this document
 
  27(c)  --  Restated Financial Data Schedule          Filed with this document
</TABLE>
- --------
*   Incorporated by reference to Form 10-K Annual Report for the fiscal year
    ended December 31, 1994
**  Incorporated by reference to Form 10-K Annual Report for the fiscal year
    ended December 31, 1995
*** Incorporated by reference to Form 10-Q Quarterly Report for the period
    ended June 30, 1998
****  Incorporated by reference to Post Effective Amendment No. 1 to
      Registration Statement on Form S-8 to Form S-4 Registration Statement
      (No. 33-50667)
 
   None of the instruments defining the rights of holders of long-term debt of
the Company and its subsidiaries (Exhibit Number 4) are being filed since the
total amount of securities authorized under any of such instruments taken
individually does not exceed 10% of the total assets of the Company and its
subsidiaries on a consolidated basis. The Company agrees to furnish a copy of
such instruments to the Commission upon request.

<PAGE>
 
                                                                    Exhibit 3(b)

                            CERTIFICATE OF AMENDMENT

                                     TO THE

                          CERTIFICATE OF INCORPORATION

                                       OF
                                        
                               MERCK & CO., INC.
                   ----------------------------------------
                    (for use by domestic corporations only)



TO:  The Secretary of State
     State of New Jersey


Pursuant to the provisions of Section 14A:7-15, Corporations, General, of the
New Jersey Statutes, the undersigned corporation executes the following
Certificate of Amendment to its Certificate of Incorporation:



1.   The name of the corporation is Merck & Co., Inc.


2.   The following amendment to the Certificate of Incorporation was approved by
     the directors of the corporation on the 24th day of November 1998:


          RESOLVED, that the first paragraph of Article IV of the Certificate of
          Incorporation be amended in its entirety to read as follows:


               "The amount of the total authorized capital stock of the
               Corporation shall be 5,410,000,000 shares consisting of
               5,400,000,000 shares of Common Stock, par value $.01 per share,
               and 10,000,000 shares of Preferred Stock, without par value,
               issuable in one or more series."


3.   The amendment to the Certificate of Incorporation will not adversely affect
     the rights or preferences of the holders of outstanding shares of any class
     or series and will not result in the percentage of authorized shares that
     remains unissued after the share division exceeding the percentage of
     authorized shares that was unissued before the share division.

4.   The class of shares subject to the division is the corporation's common
     stock, the number of shares subject to the division is 1,483,925,990 and
     the number of shares into which they will be divided is 2,967,851,980.

5.   The division of the shares is to become effective on February 16, 1999.
<PAGE>
 
6.   The effective date of this Amendment to the Certificate of Incorporation
     shall be January 25, 1999.


Dated this 13th  day of January, 1999.



                                 MERCK & CO., INC.



                                  By:  /s/ Celia A. Colbert
                                     ---------------------------
                                           Celia A. Colbert
                                           Vice President, Secretary &
                                           Assistant General Counsel


                                     - 2 -

<PAGE>
 
                                                                      Exhibit 12

                      MERCK & CO., INC. AND SUBSIDIARIES

              Computation Of Ratios Of Earnings To Fixed Charges
              --------------------------------------------------
                        (In millions except ratio data)

<TABLE>
<CAPTION>
                                                             Year Ended December 31
                                     ----------------------------------------------------------------
                                       1998            1997       1996     1995      1994      1993
                                     ---------       --------  --------  --------  --------  --------
<S>                                 <C>            <C>       <C>       <C>       <C>       <C>
Income Before Taxes                  $8,133.1        $6,462.3  $5,540.8  $4,797.2  $4,415.2  $3,102.7

Add:                                              
 One-third of rents                      56.0            47.0      41.0      28.1      36.0      35.0
 Interest expense, net                  150.6            98.2     103.2      60.3      96.0      48.0
 Preferred stock dividends               62.1            49.6      70.0       2.1         -         -
                                     --------        --------  --------  --------  --------  --------
  Earnings                           $8,401.8        $6,657.1  $5,755.0  $4,887.7  $4,547.2  $3,185.7
                                     ========        ========  ========  ========  ========  ========

One-third of rents                   $   56.0        $   47.0  $   41.0  $   28.1  $   36.0  $   35.0
 Interest expense                       205.6           129.5     138.6      98.7     124.4      84.7
 Preferred stock dividends               62.1            49.6      70.0       2.1         -         -
                                     --------        --------  --------  --------  --------  --------
  Fixed Charges                      $  323.7        $  226.1  $  249.6  $  128.9  $  160.4  $  119.7
                                     ========        ========  ========  ========  ========  ========
Ratio of Earnings                                 
 to Fixed Charges                          26              29        23        38        28        27
                                           ==              ==        ==        ==        ==        ==
</TABLE>

For purposes of computing these ratios, "earnings" consist of income before
taxes, one-third of rents (deemed by the Company to be representative of the
interest factor inherent in rents), interest expense, net of amounts
capitalized, and dividends on preferred stock of subsidiary companies.  "Fixed
charges" consist of one-third of rents, interest expense as reported in the
Company's consolidated financial statements and dividends on preferred stock of
subsidiary companies.

<PAGE>
 
                                                                      EXHIBIT 13

   Financial Section
- --------------------------------------------------------------------------------
   Contents

   Financial Review
       Description of Merck's Business ......................................30
       Competition and the Health Care Environment ..........................30
       Business Strategies ..................................................31
       Joint Ventures .......................................................31
       Foreign Operations ...................................................32
       Operating Results ....................................................32
       Environmental and Other Matters ......................................36
       Capital Expenditures .................................................37
       Analysis of Liquidity and Capital Resources ..........................37
       Recently Issued Accounting Standards .................................39
       Cautionary Factors That May Affect Future Results ....................39
       Condensed Interim Financial Data .....................................39
       Dividends Paid per Common Share ......................................39
       Common Stock Market Prices ...........................................39
   Consolidated Statement of Income .........................................40
   Consolidated Statement of Retained Earnings ..............................40
   Consolidated Statement of Comprehensive Income ...........................40
   Consolidated Balance Sheet ...............................................41
   Consolidated Statement of Cash Flows .....................................42
   Notes to Consolidated Financial Statements ...............................43
   Management's Report ......................................................52
   Report of Independent Public Accountants .................................52
   Audit Committee's Report .................................................53
   Compensation and Benefits Committee's Report .............................53
   Selected Financial Data ..................................................54

Financial Review
- --------------------------------------------------------------------------------

Description of Merck's Business

Merck is a global research-driven pharmaceutical company that discovers,
develops, manufactures and markets a broad range of human and animal health
products, directly and through its joint ventures, and provides pharmaceutical
benefit services through Merck-Medco Managed Care (Merck-Medco).

Sales
- --------------------------------------------------------------------------------
($ in millions)                                 1998          1997          1996
- --------------------------------------------------------------------------------
Elevated cholesterol .................     $ 4,694.1     $ 4,672.3     $ 4,055.9
Hypertension/heart failure ...........       4,213.5       3,855.0       3,452.6
Anti-ulcerants .......................       1,113.5       1,184.4       1,033.5
Vaccines/biologicals .................         846.7         733.6         586.8
Osteoporosis .........................         775.2         532.1         281.8
Antibiotics ..........................         743.3         774.9         822.3
Human immunodeficiency
  virus (HIV) ........................         676.3         581.7         187.8
Ophthalmologicals ....................         630.7         639.1         643.6
Animal health/crop protection ........            --         550.0       1,044.1
Other Merck products .................       1,603.2         673.5         562.3
Merck-Medco ..........................      11,601.7       9,440.3       7,158.0
- --------------------------------------------------------------------------------
                                           $26,898.2     $23,636.9     $19,828.7
================================================================================

      Human health products include therapeutic and preventive agents, generally
sold by prescription, for the treatment of human disorders. Among these are
elevated cholesterol products, which include Zocor and Mevacor;
hypertension/heart failure products which include Vasotec, the largest-selling
product among this group, Cozaar, Hyzaar, Prinivil and Vaseretic;
anti-ulcerants, of which Pepcid is the largest-selling; vaccines/biologicals, of
which M-M-R II, a pediatric vaccine for measles, mumps and rubella, Recombivax
HB (hepatitis B vaccine recombinant), and Varivax, a live virus vaccine for the
prevention of chickenpox, are the largest-selling; osteoporosis, comprised of
Fosamax, for treatment and prevention in postmenopausal women; antibiotics, of
which Primaxin and Noroxin are the largest-selling; HIV, which includes
Crixivan, a protease inhibitor for the treatment of human immunodeficiency viral
infection in adults; and opthalmologicals, of which Timoptic, Timoptic-XE and
Trusopt are the largest-selling.

      Animal health products include medicinals used to control and alleviate
disease in livestock, small animals and poultry. Crop protection includes
products for the control of crop pests and fungal disease. In July 1997, the
Company sold its crop protection business to Novartis. In August 1997, Merck and
Rhone-Poulenc combined their animal health and poultry genetics businesses to
form Merial Limited (Merial). Amounts for 1997 reflect sales for these
businesses prior to the completion of these transactions.

      Other Merck products include sales of other human pharmaceuticals,
continuing sales to divested businesses, pharmaceutical and animal health supply
sales to the Company's joint ventures and, as of July 1, 1998, supply sales to
Astra Pharmaceuticals, L.P. (APLP). (See Note 4 to the consolidated financial
statements for further information.) Also included in this category are rebates
and discounts on Merck pharmaceutical products.

      Merck-Medco primarily includes Merck-Medco sales of non-Merck products and
Merck-Medco pharmaceutical benefit services, principally managed prescription
drug programs and programs to manage patient health and drug utilization.

      Merck sells its human health products to drug wholesalers and retailers,
hospitals, clinics, government agencies and managed health care providers such
as health maintenance organizations and other institutions. The Company's
professional representatives communicate the effectiveness, safety and value of
our products to health care professionals in private practice, group practices
and managed care organizations.

Competition and the Health Care Environment

The markets in which the Company conducts its business are highly competitive
and often highly regulated. Global efforts toward health care cost containment
continue to exert pressure on product pricing and availability. In the United
States, the Company has been working with private and federal employers to slow
the increase of health care costs. Demonstrating that the Company's medicines
can help save costs in other areas and pricing flexibly across our product
portfolio have encouraged growing use of our medicines and helped offset the
effects of increasing cost pressures. Legislative bodies continue to work to
expand health care access and reduce associated costs. Although no one can
predict the outcome of legislation to accomplish the goals of reform, we are
well positioned to respond to the evolving health care environment and market
forces.

      Outside of the United States, in increasingly difficult environments
encumbered by government cost containment actions, the Company has worked with
payers to help them allocate


30  Merck & Co., Inc. 1998 Annual Report Financial Section
<PAGE>
 
scarce resources to optimize health care outcomes, limiting the potentially
detrimental effects of government actions on sales growth. In addition,
countries within the European Union (EU), recognizing the economic importance of
the research-based pharmaceutical industry and the value of innovative medicines
to society, are working with industry and the European Commission on proposals
for market deregulation.

      Several products face expiration of product patents in the near term. U.S.
product patents will expire for Vasotec and Pepcid in 2000 and for Prilosec,
which is supplied exclusively to APLP, Prinivil, for which co-marketing rights
have been licensed to a third party, Mevacor, Vaseretic and Prinzide in 2001. In
the aggregate, domestic sales of these products represent 22% of Merck human
health sales for 1998. The Company expects a significant decline in these sales
in the years 2000 through 2002 upon the loss of market exclusivity. With the
exception of Prilosec, for which the Company has U.S. rights only, a decline is
also expected in the Company's European sales for these products in the years
2000 through 2005 upon the loss of market exclusivity in European countries
throughout this period. These sales represent 7% of Merck human health sales for
1998. While the expiration of a product patent normally results in a loss of
market exclusivity, commercial benefits may continue to be derived from other
patents on processes, intermediates, compositions and formulations related to
the product, patents relating to the use of a product and, in the United States,
additional market exclusivity that may be available under federal law.

      We anticipate that the worldwide trend toward cost-containment will
continue into the new millennium, resulting in ongoing pressures on health care
budgets. As we continue to launch new products successfully, contribute to
health care debates and monitor reforms, our new products, policies and
strategies will enable us to maintain our strong position in the changing
economic environment.

Business Strategies

Consistent with our strategy to grow through volume, the Company is firmly
committed to a policy of constraining price increases, given stable market
conditions and government policies that foster innovation. Since 1990, this
policy has limited the net weighted average price changes for all human health
products in the United States to the projected general rate of inflation as
measured by the U.S. Consumer Price Index (CPI). Since its inception, this
policy has yielded a cumulative net price increase that is significantly below
the cumulative increase in the general rate of U.S. inflation.

      The Company is discovering new innovative products and developing new
indications for existing products - the result of its continuing commitment to
research. The Company is also developing innovative sales, marketing and
education techniques; establishing joint ventures, licensing agreements and
health care partnerships with large managed care organizations and other payers;
and demonstrating to payers and providers the cost-effectiveness of Merck
products. Additionally, achievement of productivity gains has become a permanent
strategy. Productivity initiatives include, at the manufacturing level,
optimizing plant utilization, implementing lowest-cost processes and improving
technology transfer between research and manufacturing, and throughout the
Company, reducing the cost of purchased materials and services, re-engineering
core and administrative processes and streamlining the organization. At the
manufacturing level, the Company expects that productivity gains will continue
to substantially offset inflation.

      To enhance its competitive position in the fast-growing area of managed
care, Merck acquired Medco Containment Services, Inc. in 1993 (renamed
Merck-Medco Managed Care). Merck-Medco provides pharmaceutical benefit services
in the United States. Merck-Medco manages prescription drug programs through its
mail service and retail pharmacy networks, and offers a series of health
management programs to help payers, providers and patients manage high-risk,
high-cost diseases. Merck-Medco sells its pharmaceutical benefit management
services to corporations, labor unions, insurance companies, Blue Cross/Blue
Shield organizations, government agencies, federal and state employee plans,
health maintenance and other similar organizations.

Joint Ventures

To expand its research base and realize synergies from combining capabilities,
opportunities and assets, the Company has formed a number of joint ventures. In
1982, Merck entered into an agreement with Astra AB (Astra) to develop and
market Astra's products under a royalty-bearing license. In 1993, the Company's
total sales of Astra products reached a level that triggered the first step in
the establishment of a joint venture business carried on by Astra Merck Inc.
(AMI), in which Merck and Astra each owned a 50% share. The joint venture,
formed in November 1994, developed and marketed most of Astra's new prescription
medicines in the United States. Joint venture sales were $1.7 billion for the
first six months of 1998, $2.3 billion for 1997 and $1.8 billion for 1996,
consisting primarily of Prilosec, the first of a class of medications known as
proton pump inhibitors, which slows the production of acid from the cells of the
stomach lining.

      On July 1, 1998, the Company and Astra completed the restructuring of the
ownership and operations of the joint venture whereby the Company acquired
Astra's interest in AMI, renamed KBI Inc. (KBI), for consideration totaling $3.1
billion. KBI's net operating assets, excluding certain product rights, were then
combined with the net assets of Astra's wholly owned subsidiary, Astra USA,
Inc., to form a new U.S. limited partnership, APLP, in which Merck maintains a
limited partner interest. For a franchise fee payment of $230.0 million, APLP
became the exclusive distributor of the products for which KBI retained rights.
Merck earns certain partnership returns as well as ongoing revenue based on
sales of current and future KBI products. The partnership returns include a
priority return, a fixed return and certain variable returns which are based, in
part, upon sales of certain former Astra USA, Inc. products. The fixed return
represents accretion of the carrying value of Merck's limited partnership
interest from its initial carrying value up to its liquidating net worth, which
is being recognized into income over 10 years on a straight-line basis. For a
payment of $443.0 million, Astra purchased an option to buy Merck's interest in
the KBI products in 2008, 2012 or 2016, excluding Merck's interest in the
gastrointestinal medicines Prilosec and perprazole. (See Note 4 to the
consolidated financial statements for further information.)


                      Merck & Co., Inc. 1998 Annual Report Financial Section  31
<PAGE>
 
      In December 1998, Astra announced plans to merge with Zeneca Group Plc. If
this proposed merger is completed, Astra will be required to make one-time
payments to Merck totaling approximately $1.8 billion for the relinquishment of
certain rights, including option rights to future Astra products with no
existing or pending U.S. patents at the time of the merger. This merger would
also trigger a partial redemption of Merck's limited partnership interest in
2008. Furthermore, upon completion of the merger, Astra's option to buy Merck's
interest in the KBI products would only be exercisable in 2010 and Merck would
obtain the right to require Astra to purchase such interest in 2008.

      In 1989, Merck formed a joint venture with Johnson & Johnson to develop
and market a broad range of nonprescription medicines for U.S. consumers. This
50% owned joint venture was expanded into Europe in 1993, and into Canada in
1996. Sales of joint venture products were as follows:

                                                1998          1997          1996
- --------------------------------------------------------------------------------
Gastrointestinal products ............       $ 387.2       $ 386.3       $ 420.5
Other products .......................         127.0          97.4         109.7
- --------------------------------------------------------------------------------
                                             $ 514.2       $ 483.7       $ 530.2
================================================================================

      In 1991, Merck and E.I. du Pont de Nemours and Company (DuPont) formed an
independent, research-driven, worldwide pharmaceutical joint venture, The DuPont
Merck Pharmaceutical Company (DMPC), equally owned by each party. DuPont
contributed its entire pharmaceutical and radiopharmaceutical imaging agents
businesses, and provided administrative services. Merck contributed cash and
European marketing rights to several of its prescription medicines, and provided
research and development and international industry expertise. Joint venture
sales were $686.2 million for the first six months of 1998, and $1.3 billion for
1997 and 1996, consisting primarily of cardiovascular, radiopharmaceutical and
central nervous system products. On July 1, 1998, the Company sold its one-half
interest in DMPC to DuPont for $2.6 billion in cash. (See Note 3 to the
consolidated financial statements for further information.)

      In 1994, Merck and Pasteur Merieux Connaught established a 50% owned joint
venture to market vaccines and collaborate in the development of combination
vaccines, for distribution in Europe. Sales of joint venture products were as
follows:

                                              1998           1997           1996
- --------------------------------------------------------------------------------
Hepatitis vaccines ................        $ 189.0        $ 216.2        $ 242.0
Viral vaccines ....................           64.6           63.3           70.2
Other vaccines ....................          306.8          301.8          350.8
- --------------------------------------------------------------------------------
                                           $ 560.4        $ 581.3        $ 663.0
================================================================================

      In August 1997, Merck and Rhone-Poulenc combined their animal health and
poultry genetics businesses to form Merial, a fully integrated, stand-alone
joint venture, equally owned by each party. Merial is the world's largest
company dedicated to the discovery, manufacture and marketing of veterinary
pharmaceuticals and vaccines. Merck contributed developmental research
personnel, sales and marketing activities, and animal health products, as well
as its poultry genetics business. Rhone-Poulenc contributed research and
development, manufacturing, sales and marketing activities, and animal health
products, as well as its poultry genetics business. The formation of Merial has
not had a material impact on comparability of net income. Animal health sales
reported in Merck's 1997 consolidated sales were $448.3 million prior to August
1. Sales of joint venture products were as follows:

                                                          1998              1997
- --------------------------------------------------------------------------------
Avermectin products .......................           $  616.4          $  308.6
Fipronil products .........................              300.8              83.1
Other products ............................              842.2             354.6
- --------------------------------------------------------------------------------
                                                      $1,759.4          $  746.3
================================================================================

Foreign Operations

The Company's operations outside the United States are conducted primarily
through subsidiaries. Sales of Merck human health products by subsidiaries
outside the United States were 43% of Merck human health sales in 1998, and 46%
and 47% in 1997 and 1996, respectively. The 1998 percentage was affected by
increased domestic supply sales to APLP, as a result of the restructuring of
AMI.

                          DISTRIBUTION OF 1998 FOREIGN
                               HUMAN HEALTH SALES

                                   [GRAPHIC]
                                                        Splits
                                                        ------
                    Western Europe                        54%
                    Asia/Pacific                          24%
                    Other Foreign                         22%
                                                        ------
                        Total                            100%

      The Company's worldwide business is subject to risks of currency
fluctuations and governmental actions. The Company does not regard these risks
as a deterrent to further expansion of its operations abroad. However, the
Company closely reviews its methods of operations and adopts strategies
responsive to changing economic and political conditions.

      Within the EU, there has been an evolution toward a single market in
pharmaceuticals, for which Economic and Monetary Union, including the adoption
of the euro as a single currency, marks an important step. The Company has
recognized the strategic significance of this development and will adopt the
euro in 1999. In this way, we are demonstrating our support for the European
Community's industrial policy, while working toward the EU's goal of a
competition-driven market that will enhance access to quality healthcare for
European citizens.

      In recent years, Merck has been expanding its operations in countries
located in Latin America, the Middle East, Africa, Eastern Europe and Asia
Pacific where changes in government policies and economic conditions are making
it possible for Merck to earn fair returns. Businesses in these developing
areas, while sometimes less stable, offer important opportunities for growth
over time.

Operating Results

Total sales for 1998 increased 14% from 1997, including a three point increase
attributable to supply sales to APLP, as a result of the restructuring of AMI.
The effect of a strengthening U.S. dollar 


32  Merck & Co., Inc. 1998 Annual Report Financial Section
<PAGE>
 
against foreign currencies decreased 1998 sales growth by two percentage points.
Sales growth for 1998 was also affected by the 1997 formation of the Merial
joint venture and divestiture of the crop protection business. Adjusting for
these effects, sales grew 16% in 1998 in total and 13% on a volume basis. Total
sales for 1997 increased 19% from 1996. Foreign exchange reduced 1997 sales
growth by two percentage points. Sales growth for 1997 was affected by the
formation of the Merial joint venture and the divestiture of the crop protection
business. Adjusting for these effects, 1997 sales grew 22% in total and 19% on a
volume basis.

                    COMPONENTS OF HUMAN HEALTH SALES GROWTH

                                   [GRAPHIC]

             TOTAL SALES         SALES VOLUME      NET PRICING       FOREIGN
               GROWTH               GROWTH           ACTIONS      EXCHANGE RATES
               ------               ------           -------      --------------

1994             8.4%                 7.9%            -0.4%            0.9% 
1995            13.0                 10.9             -0.5             2.6  
1996            17.7                 19.2              0.4            -1.9 
1997            15.0                 17.6              0.3            -2.9 
1998            10.9                 14.1               --            -3.2 

This chart illustrates the effects of price, volume and exchange on sales of
Merck human health products. Growth for 1994 and 1995 has been adjusted for the
effect of the Astra Merck joint venture formation. Growth for 1998 includes a
five point increase attributable to the AMI restructuring. The human health
business has grown predominantly through sales volume over the last five years.
Price had essentially no effect on sales growth, while the effect of exchange
has varied over the same period.

      In 1998, sales of Merck human health products grew 11%, including a five
point increase attributable to the restructuring of AMI. Foreign exchange rates
had a three percentage point unfavorable effect on sales growth, while price
changes had essentially no effect. In measuring these effects, changes in the
value of foreign currencies are calculated net of price increases in
hyperinflationary countries, principally in Latin America. Domestic sales growth
was 17%, including a nine point increase attributable to the restructuring of
AMI, while foreign sales grew 4% including a seven percentage point unfavorable
effect from exchange. The unit volume growth from sales of Merck human health
products was paced by established products, including Zocor, Prinivil, Proscar
and M-M-R II, newer products, including Cozaar, Hyzaar, Fosamax, Crixivan,
Varivax, Vaqta, Comvax and Trusopt, as well as the 1998 launches of Singulair,
Propecia, Maxalt, Cosopt and Aggrastat.

      Together, Merck's cholesterol-lowering agents, Zocor and Mevacor,
continued to hold more than 40% of the worldwide statin market. The
cholesterol-lowering market continues to grow rapidly, driven primarily by
growth of more than 25% annually in the statin category, yet today, even in the
U.S. market, only about one-third of eligible patients are receiving treatment.
In 1998, Zocor continued its strong volume growth and continues to be the most
widely used cholesterol-lowering medicine worldwide. In July 1998, the U.S. Food
and Drug Administration (FDA) approved a new 80 mg tablet of Zocor, which
lowered LDL ("bad") cholesterol in clinical studies by a mean of 47%. In
addition, the prescribing information for Zocor in the United States was changed
to recommend the 20 mg tablet as the usual starting dose. Merck has demonstrated
its confidence in the efficacy of the new dosage range by introducing the "Get
to Goal Guarantee" whereby patients can receive money back if they do not
achieve the cholesterol goal set by their physicians while on Zocor.

      Vasotec and Prinivil, Merck's angiotensin converting enzyme (ACE)
inhibitors for high blood pressure, heart failure and other cardiovascular
disorders, continue to be among the world's most widely prescribed branded
anti-hypertensives. Together, they hold about 30% of the worldwide market for
ACE inhibitors. Prinivil, with its convenient once-daily dosing in hypertension,
heart failure and acute myocardial infarction, continues to grow well above the
rate of the overall ACE inhibitor market. In the United States, Vasotec is the
only ACE inhibitor indicated for the treatment of high blood pressure,
asymptomatic left ventricular dysfunction and heart failure, and the only ACE
inhibitor indicated to reduce deaths due to symptomatic heart failure,
regardless of the underlying cause.

      Proscar provides long-term disease management of symptomatic benign
prostate enlargement, a disease that affects more than 50% of men age 60 and
older. The results from the Proscar Long-Term Efficacy and Safety Study (PLESS),
the largest and longest study ever conducted in benign prostate hyperplasia
(BPH) involving more than 3,000 men, showed that in men with urinary symptoms
and enlarged prostates, Proscar reduced the risk of acute urinary retention by
57% and the need for prostate surgery by 55%. In March 1998, the FDA granted a
new indication for Proscar that made it the only drug for symptomatic BPH
indicated to reduce the risk of acute urinary retention and the need for
BPH-related surgery.

      Cozaar and Hyzaar (a combination of Cozaar and the diuretic
hydrochlorothiazide), Merck's newest antihypertensive drugs and among Merck's
fastest-growing products, were the first in a new class of drugs that block a
potent hormone called angiotensin II, resulting in gradual, smooth, 24-hour
blood pressure reduction. Cozaar has been approved in 78 countries, including
its recent launch in Japan. Ongoing research has reinforced and expanded the
medical value of these products, which have been adopted faster than any new
antihypertensive product launched this decade because of its excellent
tolerability profile and proven efficacy in treating high blood pressure. Cozaar
is also the only product in its class cleared for use in the treatment of heart
failure in any market. Currently, approval of this indication has been received
in 15 countries and applications are pending in other countries. The Company has
not yet filed an application for this indication in the United States.

      Fosamax, Merck's nonhormonal medicine to treat and prevent postmenopausal
osteoporosis and reduce the risk of fractures due to osteoporosis, continued to
record strong growth in 1998, and is the leading nonhormonal treatment for
osteoporosis worldwide. Research continues to show the importance of Fosamax in
treating and preventing postmenopausal osteoporosis and fractures due to
bone-thinning. Two year results from a six year Early Postmenopausal
Interventional Cohort trial showed that Fosamax is an effective nonhormonal
alternative to hormone replacement therapy for stopping bone loss and building
bone in postmenopausal women at risk for osteoporosis. Data from the landmark
Fracture Intervention Trial confirmed the ability of Fosamax to reduce, by
nearly half, the risk of hip and spine fractures in postmenopausal women with
osteoporosis.


                     Merck & Co., Inc. 1998 Annual Report  Financial Section  33
<PAGE>
 
      Crixivan, Merck's protease inhibitor for the treatment of HIV infection,
is sold in more than 80 countries. New data from a two year landmark study
demonstrated sustained anti-HIV effects, suppressing HIV below detection level
in nearly 75% of patients, when Crixivan is taken in triple therapy. Preliminary
results from a Merck study, presented in November 1998 at the annual meeting of
the Infectious Diseases Society of America in Denver, showed that the
twice-daily combination of Crixivan with the protease inhibitor nelfinavir may
be a potent and convenient regimen for HIV patients.

      Varivax, a live-virus vaccine for protection against chickenpox in healthy
individuals age 12 months and older who have not had the disease, continued to
record strong growth in 1998. It is the first and only chickenpox vaccine
available in the United States.

      Vaqta, Merck's vaccine for the prevention of hepatitis A in persons age
two years and older, continued its strong growth in 1998. Hepatitis A is a
highly contagious virus, spread through contaminated food or water, which
attacks the liver and can cause victims to be ill for several weeks.

      Comvax, Merck's newest vaccine, a combination of the antigenic components
of two existing Merck vaccines, PedvaxHIB and Recombivax HB, recorded strong
growth in 1998. Comvax is the first combination product indicated for the
vaccination of infants, age two months and older, against both invasive
Haemophilus influenzae type b disease and hepatitis B virus. The combination
reduces the number of injections required to immunize children against the two
infections.

      In 1998, Merck launched a series of new and unique products, many
representing innovative treatments for conditions afflicting millions, including
Singulair for chronic asthma, Propecia for male pattern hair loss, Maxalt for
migraine headaches, Cosopt, a combination product of Timoptic and Trusopt, for
patients with elevated intraocular pressure who did not respond adequately to
beta-blockers alone, and Aggrastat, a platelet blocker for preventing cardiac
ischemic events.

      Singulair, Merck's new once-a-day tablet for controlling chronic asthma in
adults and children age six and older, has quickly become the leader in the U.S.
leukotriene antagonist class. The product has been launched in 38 countries
including the United States, United Kingdom, Spain, Germany, Sweden and Denmark.
In clinical studies, Singulair improved asthma control in many patients by
significantly decreasing asthma attacks, helping to prevent day- and night-time
symptoms and reduce reliance on other asthma medications, such as
bronchodilators and inhaled steroids.

      Propecia, the first and only tablet to treat male pattern hair loss, was
introduced in the United States and 11 other countries in 1998, with launches
pending in 13 more. In clinical studies, 83% of men treated with Propecia
maintained their current hair count and 66% grew visible new hair. Since its
introduction, U.S. physicians have written more than one million prescriptions
for Propecia, and more than 400,000 men have started treatment.

      Maxalt, Merck's new treatment for migraine headaches, has been launched in
11 countries including the United States, United Kingdom, Sweden, the
Netherlands and Mexico, making it the fastest growing oral migraine medication
in the U.S. and other key markets. Maxalt provides fast and effective relief of
the debilitating headache pain and other symptoms such as nausea and sensitivity
to light and noise that often accompany a migraine attack. Maxalt is the first
and only migraine medicine available in both conventional tablets and
convenient, rapidly dissolving oral tablets, which disintegrate within seconds
on the tongue without liquids.

      Aggrastat, a platelet blocker, was approved for the treatment of acute
coronary syndrome, including patients with unstable angina/non-Q-wave myocardial
infarction who are managed medically and those undergoing angioplasty or
atherectomy. Clinical data showed that in combination with standard therapy,
Aggrastat reduced the risk of heart attacks and death by 30% at 30 days, and
reduced the overall risk of heart attacks by 47% at seven days. Aggrastat has
been launched in eight countries including the United States, Switzerland,
Germany, Brazil and Mexico.

      A group of mature products, including Pepcid, Timoptic, Noroxin, Mefoxin,
Moduretic and Aldomet, while still contributing to 1998 revenues, declined in
unit volume due to generic and therapeutic competition.

      In 1997, sales of Merck human health products grew 15%. Foreign exchange
rates had a three percentage point unfavorable effect on sales growth, while
price changes had essentially no effect. Domestic sales growth was 17%, while
foreign sales grew 13% including a six percentage point unfavorable effect from
exchange. The unit volume growth from sales of Merck human health products was
paced by Zocor, Vasotec, Vaseretic, Prinivil, Pepcid, Recombivax HB and M-M-R
II, the newer products, including Crixivan, Cozaar, Hyzaar, Fosamax, Trusopt,
Varivax and Vaqta, and the 1997 launch of Comvax in the United States.

      Sales of animal health products were affected by the formation of the
Merial joint venture with Rhone-Poulenc in August of 1997. Prior to this, a weak
worldwide cattle economy slowed sales growth. Crop protection sales were lower
in 1997 due to the divestiture of this business.

      Merck-Medco sales contributed significantly to 1998 and 1997 sales growth.
By continuing to invest in the development of important clinical programs,
enhanced information management systems and communications technologies,
Merck-Medco has strengthened its leadership position in managing prescription
drug care and high-cost, high-risk diseases. In 1998, Merck-Medco demonstrated
the value of its services by gaining important new customers in all market
segments, including employers, managed care organizations, Blue Cross/Blue
Shield plans, unions and government programs. The number of prescriptions
managed by Merck-Medco grew to 322 million in 1998, up 11% from 291 million
prescriptions in 1997.

Costs, Expenses and Other
- --------------------------------------------------------------------------------
($ in millions)            1998   Change           1997    Change          1996
- --------------------------------------------------------------------------------
Materials and
  production ........ $13,925.4     +18%      $11,790.3      +27%     $ 9,319.2
Marketing and
  administrative ....   4,511.4      +5%        4,299.2      +12%       3,841.3
Research and
  development .......   1,821.1      +8%        1,683.7      +13%       1,487.3
Acquired
  research ..........   1,039.5        *             --       --             --
Equity income
  from affiliates ...    (884.3)    +21%         (727.9)     +21%        (600.7)
Gains on sales
  of businesses .....  (2,147.7)       *         (213.4)        *            --
Other (income)
  expense, net ......     499.7     +46%          342.7      +42%         240.8
- --------------------------------------------------------------------------------
                      $18,765.1      +9%      $17,174.6      +20%     $14,287.9
================================================================================
*Over 100%


34  Merck & Co., Inc. 1998 Annual Report  Financial Section
<PAGE>
 
      In 1998, materials and production costs increased 18%. Adjusting for the
effects of the 1997 formation of the Merial joint venture and sale of the crop
protection business, materials and production costs increased 19%, compared to a
16% sales growth rate on the same basis. Adjusting for the aforementioned
effects, and excluding exchange and inflation, these costs increased 12%,
compared to a 13% unit sales volume gain in 1998. The lower growth rate in these
costs over the sales volume growth is primarily attributable to the favorable
effect of the AMI restructuring. In 1997, materials and production costs
increased 27%. Adjusting for the effects of the 1997 formation of the Merial
joint venture and the divestiture of the crop protection business, materials and
production costs increased 28%, compared to a 22% sales growth rate on the same
basis. Adjusting for the aforementioned effects, and excluding exchange and
inflation, these costs increased 21%, compared to a 19% unit sales volume gain
in 1997.

      Marketing and administrative expenses increased 5% in 1998. Adjusting for
the effects of the 1997 formation of the Merial joint venture and sale of the
crop protection business, marketing and administrative expenses increased 9%.
Adjusting for the aforementioned effects, and excluding exchange and inflation,
these expenses also increased 9%. The increase in marketing and administrative
expenses in 1998 primarily reflects the commitment of resources to support
recent product launches, including five new products in 1998, expansion of sales
forces in the United States and several key international markets, and
investments in information technology initiatives by Merck-Medco, which are
setting new standards for the management of major diseases. Marketing and
administrative expenses increased 12% in 1997. Adjusting for the effects of the
1997 formation of the Merial joint venture and the divestiture of the crop
protection business, marketing and administrative expenses increased 15%.
Adjusting for the aforementioned effects, and excluding exchange and inflation,
these expenses increased 16%, primarily due to the commitment of resources to
support 1995 through 1997 product launches, pre-launch spending for new products
launched in 1998, expansion of sales forces in the United States and Europe, and
investments in health management programs and information technology initiatives
by Merck-Medco. Marketing and administrative expenses as a percentage of sales
were 17% in 1998, 18% in 1997 and 19% in 1996. The improvement in these ratios
reflects the lower marketing and administrative costs relative to Merck-Medco
sales, continuing cost controls and productivity improvements and the favorable
effect of the AMI restructuring.

      Research and development expenses increased 8% in 1998. Adjusting for the
effects of the 1997 formation of the Merial joint venture and sale of the crop
protection business, these expenses increased 10%. Adjusting for the
aforementioned effects, and excluding exchange and inflation, these expenses
increased 8%. Research and development expenses increased 13% in 1997. Adjusting
for the effects of the 1997 formation of the Merial joint venture and sale of
the crop protection business, these expenses increased 15%. Adjusting for the
aforementioned effects, and excluding the effects of exchange and inflation,
these expenses increased 13%.

      Research and development in the pharmaceutical industry is inherently a
long-term process. The following data show an unbroken trend of year-to-year
increases in research and development spending. For the period 1989 to 1998, the
compounded annual growth rate in research and development was 11%. Research and
development expenses for 1999 are estimated to approximate $2.1 billion.

                                R&D EXPENDITURES
                                 ($ in millions)

                                   [GRAPHIC]

                       Year             Total R&D Expenditures
                       ----             ----------------------

                       1989                    $  751
                       1990                       854
                       1991                       988
                       1992                     1,112
                       1993                     1,173
                       1994                     1,231
                       1995                     1,331
                       1996                     1,487
                       1997                     1,684
                       1998                     1,821

      In 1998, in connection with the restructuring of AMI, the Company recorded
a $1.04 billion charge for acquired research associated with 10 product
candidates in Phase II or later stages of development and U.S. rights to future
Astra products which have not yet entered Phase II, for which, at the
acquisition date, commercial viability had not been established. (See Note 4 to
the consolidated financial statements for further information.)

      Equity income from affiliates reflects the favorable performance of our
joint ventures, and in the second half of 1998, partnership returns from APLP,
which are recorded on a pretax basis, and the absence of equity income from DMPC
following the Company's sale of its one-half interest.

      In the third quarter of 1998, the Company recorded a pretax gain of $2.15
billion ($1.25 billion after tax) on the sale of its one-half interest in DMPC.
(See Note 3 to the consolidated financial statements for further information.)
This gain was substantially offset on an after-tax basis by a $1.04 billion
pretax and after-tax charge for acquired research in connection with the
restructuring of AMI and $338.6 million of pretax other non recurring charges
($193.1 million after tax). These other charges, which are included in Other
(income) expense, net, were primarily for environmental remediation costs and
asset write-offs, principally deferred start-up costs which were expensed in
accordance with the Company's third quarter adoption of Statement of Position
No. 98-5, "Reporting on the Costs of Start-up Activities."

      In 1997, the Company recorded a pretax gain of $213.4 million on the sale
of its crop protection business. (See Note 3 to the consolidated financial
statements for further information.) This gain was substantially offset by
$207.3 million of pretax nonrecurring charges included in Other (income)
expense, net, primarily for the loss on sale of assets, endowment of The Merck
Company Foundation and environmental remediation costs.


                     Merck & Co., Inc. 1998 Annual Report  Financial Section  35
<PAGE>
 
      In 1998, other expense, net, increased primarily due to $338.6 million of
nonrecurring charges, increased amortization of goodwill and other intangibles
arising from the restructuring of AMI, increased minority interest expense
reflecting dividends paid to Astra on preferred stock of a subsidiary and higher
interest expense. This increase was partially offset by higher interest income
benefiting from the proceeds from the sale of the Company's one-half interest in
DMPC and $207.3 million of non-recurring charges recorded in 1997, which
substantially offset the gain on the sale of the crop protection business. In
1997, other expense, net, increased primarily due to the aforementioned $207.3
million of nonrecurring charges and lower exchange gains resulting from
translation of the Company's balance sheet. This increase was partially offset
by realized gains on security sales, higher interest income, lower interest
expense and lower income allocable to minority interests. (See Note 14 to the
consolidated financial statements for further information.)

Earnings
- --------------------------------------------------------------------------------
($ in millions except
per share amounts)         1998   Change           1997    Change          1996
- --------------------------------------------------------------------------------
Net income ............$5,248.2     +14%       $4,614.1      +19%      $3,881.3
  As a % of sales .....    19.5%                   19.5%                   19.6%
  As a % of average
   total assets .......    18.2%                   18.5%                   16.1%
Earnings per common
  share assuming
  dilution ............   $2.15     +15%          $1.87      +20%         $1.56
================================================================================

      Net income was up 14% in 1998 and 19% in 1997. Net income as a percentage
of sales was 19.5% in 1998 and 1997, compared to 19.6% in 1996. The decline in
the ratio from 1996 is principally due to a higher growth rate in Medco's
historically lower-margin business and the commitment of resources to support
recent product launches, offset, in part, by the growth in Merck's human health
business, and manufacturing, marketing, and general and administrative
productivity improvements. Foreign currency exchange had a four percentage point
unfavorable effect as compared to a two percentage point unfavorable effect in
1997. The Company's effective income tax rate in 1998 was 35.5%, compared to
28.6% in 1997 and 30.0% in 1996. The higher effective rate in 1998 was primarily
driven by the impact of nonrecurring items, principally the nondeductibility of
the charge for acquired research in connection with the restructuring of AMI and
the state tax impact of the gain on the sale of the Company's one-half interest
in DMPC. The increased tax rate substantially offset the growth in pretax income
from these items, resulting in no significant effect on net income growth. The
lower effective tax rate in 1997 versus 1996 primarily relates to joint
ventures, which also affected pretax income growth. Specifically, pretax income
growth was reduced by the Company's share of the increase in taxes related to
certain of the Company's joint ventures. The impact on pretax growth, however,
was offset by a corresponding reduction in the Company's tax rate, resulting in
no effect on net income growth. Net income as a percentage of average total
assets was 18.2% in 1998, 18.5% in 1997 and 16.1% in 1996, with the improvement
from 1996 attributable to the continued growth in operations and the Company's
asset management efforts. Earnings per common share assuming dilution grew 15%
in 1998, compared to 20% in 1997. In 1998 and 1997, earnings per common share
assuming dilution increased at a faster rate than net income as a result of
treasury stock purchases.

                  DISTRIBUTION OF 1998 SALES AND EQUITY INCOME
                         (excluding nonrecurring items)

                                    [GRAPHIC]

                                                          Splits
                                                          ------
               Raw Materials and Production Costs           50%
               Operating Expenses                           24%
               Taxes and Net Interest                        7%
               Dividends                                     9%
               Retained Earnings                            10%
                                                          ------
                    Total                                  100%
                                                          ======
     
Environmental and Other Matters

The Company believes that it is in compliance in all material respects with
applicable environmental laws and regulations. In 1998, the Company incurred
capital expenditures of approximately $56.5 million for environmental protection
facilities. Capital expenditures for this purpose are forecasted to exceed
$550.0 million for the years 1999 through 2003. In addition, the Company's
operating and maintenance expenditures for pollution control were approximately
$83.4 million in 1998. Expenditures for this purpose for the years 1999 through
2003 are forecasted to exceed $484.0 million.

      The Company is a party to a number of proceedings brought under the
Comprehensive Environmental Response, Compensation and Liability Act, commonly
known as Superfund, as well as under other federal and state statutes. While it
is not feasible to predict or determine the outcome of these proceedings,
management does not believe that they should result in a materially adverse
effect on the Company's financial position, results of operations, liquidity or
capital resources. The Company is also remediating environmental contamination
resulting from past industrial activity at certain of its sites. The Company has
taken an active role in identifying and providing for these costs; and,
therefore, management does not believe that these expenditures should result in
a materially adverse effect on the Company's financial position, results of
operations, liquidity or capital resources. Expenditures for remediation and
environmental liabilities were $16.7 million in 1998, and are estimated at
$220.0 million for the years 1999 through 2003. These amounts do not consider
potential recoveries from insurers or other parties.

      In 1994, the Company, along with other pharmaceutical manufacturers and
pharmaceutical benefits managers (PBMs), received a notice from the Federal
Trade Commission (FTC) that it intended to investigate agreements, alliances,
activities and acquisitions involving pharmaceutical manufacturers and PBMs. In
August 1998, the Company and Merck-Medco reached an agreement with the FTC
which, subject to final approval, resolves their portion of the investigation.
The agreement formalizes the policies and practices the Company and Merck-Medco
voluntarily adopted over four years ago governing the operation of their
businesses. The agreement will not affect how the Company and Merck-Medco
currently compete in the marketplace, serve their customers or conduct business
with third parties. Accordingly, the Company does not believe that the agreement
will have a materially adverse effect on the Company's financial position,
liquidity or results of operations.


36  Merck & Co., Inc. 1998 Annual Report  Financial Section
<PAGE>
 
      In 1996, the Company, along with other pharmaceutical manufacturers,
received a notice from the FTC that it was conducting an investigation into
pricing practices. The Company has cooperated fully with the FTC in this
investigation, and believes that it is currently operating in all material
respects in accordance with applicable standards. While it is not feasible to
predict or determine the outcome of this investigation, management does not
believe that it should result in a materially adverse effect on the Company's
financial position, results of operations or liquidity.

      The continued efficient operation of the Company's business will be
dependent upon the ability of its systems to process date sensitive information
in the Year 2000. As a result, the Company initiated a program in 1996 to
inventory all critical systems, assess the impact of Year 2000 noncompliance,
develop plans to remediate or replace noncompliant systems and assess the
readiness of key third parties. The inventory and assessment phases are complete
for internal information technology (IT) systems and the Company is
approximately 75% complete with the remediation phase as of December 31, 1998.
The evaluation and remediation phases for non-IT systems (e.g. building, process
and factory control systems) are currently underway. Although the Company has
designed these programs to properly prepare its systems for the Year 2000, there
can be no assurance that the Company will not experience business disruptions or
incur material costs caused by the failure to detect and remediate all instances
of Year 2000 noncompliance in its systems. Failure to complete these programs as
planned could result in the corruption of data, hardware or equipment failures
or the inability to manufacture products or conduct other business activities,
all of which could have a material impact on the Company's business, results of
operations or financial position. Contingency plans (including the substitution
of systems, use of manual methods and other means to prevent the failure of
critical systems from having a material effect on the Company) are under
development, particularly for high risk areas such as those involving supplier
and product management.

      In addition to risks associated with internal systems, the Company has
relationships with, and is to varying degrees dependent upon, third parties that
provide the Company with information, goods and services. These include
financial institutions, suppliers, vendors, utilities, research partners and
governmental entities, as well as customers and distributors. If a significant
number of these third parties experience failures in their systems due to Year
2000 noncompliance, it could affect the Company's ability to process
transactions, manufacture products, or engage in other business activities.
While some of these risks are outside of the Company's control, the Company has
instituted programs, including internal records review and external
questionnaires and supplier audits, to identify key third parties, assess their
level of Year 2000 compliance, update contracts, develop supplier-based
contingency plans and address any noncompliance issues.

      All critical aspects of the Company's Year 2000 compliance program are
expected to be completed by the end of the third quarter 1999. Total costs to
resolve the Year 2000 issue are not expected to be material to the Company's
financial position, results of operations or cash flows.

Capital Expenditures

Capital expenditures were $2.0 billion in 1998 and $1.4 billion in 1997.
Expenditures in the United States were $1.4 billion in 1998 and $1.1 billion in
1997. Expenditures during 1998 included $851.5 million for production
facilities, $505.0 million for research and development facilities, $56.5
million for environmental projects, and $560.4 million for administrative,
safety and general site projects. Capital expenditures approved but not yet
spent at December 31, 1998 were $2.1 billion. Capital expenditures for 1999 are
estimated to be $2.3 billion.

      Depreciation was $700.0 million in 1998 and $602.4 million in 1997, of
which $512.3 million and $437.3 million, respectively, applied to locations in
the United States.

                              CAPITAL EXPENDITURES
                                  ($ in millions)

                                    [GRAPHIC]

                      YEAR          TOTAL CAPITAL EXPENDITURES
                      ----          --------------------------

                      1989                    $  433   
                      1990                       671   
                      1991                     1,042 
                      1992                     1,067 
                      1993                     1,013 
                      1994                     1,009 
                      1995                     1,005 
                      1996                     1,197 
                      1997                     1,449 
                      1998                     1,973 

Analysis of Liquidity and Capital Resources

Cash provided by operations continues to be the Company's primary source of
funds to finance operating needs and capital expenditures. In 1998, pretax cash
flows from operations were $7.5 billion, reflecting the continued growth of the
Company's earnings. This cash was used to fund capital expenditures of $2.0
billion, to pay Company dividends of $2.3 billion and to partially fund the
purchase of treasury shares. At December 31, 1998, the total of worldwide cash
and investments was $7.0 billion, including $3.4 billion in cash, cash
equivalents and short-term investments, and $3.6 billion of long-term
investments. The above totals include $1.1 billion in cash and investments held
by Banyu Pharmaceutical Co., Ltd., in which the Company has a 50.87% ownership
interest.

Selected Data

- --------------------------------------------------------------------------------
($ in millions)                            1998            1997            1996
- --------------------------------------------------------------------------------
Working capital ...................... $4,159.7        $2,644.4        $2,897.4
Total debt to total liabilities                                       
  and equity .........................     12.1%            8.7%            7.3%
Cash provided by operations                                           
  to total debt ......................    1.4:1           2.8:1           3.1:1
================================================================================

      Working capital levels are more than adequate to meet the operating
requirements of the Company. Working capital in 1998 reflects proceeds of $2.6
billion from the sale of the Company's one-half interest in DMPC and proceeds
from the issuance of a $1.38 billion 40-year note to Astra. These proceeds were
used to fund a portion of the Company's stock repurchase program and for other
general corporate purposes.

      In 1998, debt levels were affected by the issuances of the $1.38 billion
note to Astra and two $500.0 million debentures, increasing the ratio of total
debt to total liabilities and equity.


                     Merck & Co., Inc. 1998 Annual Report  Financial Section  37
<PAGE>
 
The favorable ratio of cash provided by operations to total debt, although
impacted by these debt issuances, still reflects the ability of the Company to
cover its debt obligations.

      In July 1998, the Board of Directors approved purchases of up to $5.0
billion of Merck shares. From 1996 to 1998, the Company purchased $8.4 billion
of treasury shares under previously authorized completed programs, and $.3
billion under the 1998 program. Total treasury stock purchased in 1998 was $3.6
billion. For the period 1989 to 1998, the Company has purchased 436.8 million
shares at a total cost of $13.3 billion.

      In 1997, Merck filed a $1.5 billion shelf registration with the Securities
and Exchange Commission for the issuance of debt securities, increasing
available capacity under such filings to $1.7 billion. In both February and
November 1998, the Company issued $500.0 million of 30-year debentures under the
shelf, bearing coupons of 6.4% and 6.0%, respectively, payable semiannually. The
remaining capacity under the shelf is $.7 billion at December 31, 1998. Also in
1997, the Company established a $1.5 billion Euro Medium Term Note program,
under which no securities have been issued. Proceeds from the sale of these
securities are to be used for general corporate purposes.

      The Company's strong financial position, as evidenced by its triple-A
credit ratings from Moody's and Standard & Poor's on outstanding debt issues,
provides a high degree of flexibility in obtaining funds on competitive terms.
The ability to finance ongoing operations primarily from internally generated
funds is desirable because of the high risks inherent in research and
development required to develop and market innovative new products and the
highly competitive nature of the pharmaceutical industry.

      A significant portion of the Company's cash flows are denominated in
foreign currencies. The Company relies on sustained cash flows generated from
foreign sources to support its long-term commitment to U.S. dollar-based
research and development. To the extent the dollar value of cash flows is
diminished as a result of a strengthening dollar, the Company's ability to fund
research and other dollar-based strategic initiatives at a consistent level may
be impaired. To protect against the reduction in value of foreign currency cash
flows, the Company has instituted balance sheet and revenue hedging programs to
partially hedge this risk.

      The objective of the balance sheet hedging program is to protect the U.S.
dollar value of foreign currency denominated net monetary assets from the
effects of volatility in foreign exchange that might occur prior to their
conversion to U.S. dollars. To achieve this objective, the Company will hedge
foreign currency risk on monetary assets and liabilities where hedging is cost
beneficial. The Company seeks to fully hedge exposure denominated in developed
country currencies, such as those of Japan, Germany, France and Canada, and will
either partially hedge or not hedge at all exposure in other currencies,
particularly exposure in hyperinflationary countries where hedging instruments
may not be available at any cost. The Company will minimize the effect of
exchange on unhedged exposure, principally by managing operating activities and
net asset positions at the local level. The Company manages its net asset
exposure principally with forward exchange contracts. These contracts enable the
Company to buy and sell foreign currencies in the future at fixed exchange
rates. For net monetary assets hedged, forward contracts offset the consequences
of changes in foreign exchange on the amount of U.S. dollar cash flows derived
from the net assets. Contracts used to hedge net monetary asset exposure have
average maturities at inception of less than one year. A sensitivity analysis to
changes in the value of the U.S. dollar on foreign currency denominated
derivatives and monetary assets and liabilities indicated that if the U.S.
dollar uniformly weakened by 10% against all currency exposures of the Company
at December 31, 1998 and 1997, Income before taxes would have declined by $53.9
million and $10.9 million, respectively. The balance sheet hedging program has
significantly reduced the volatility of U.S. dollar cash flows derived from
foreign currency denominated net monetary assets. The cash flows from these
contracts are reported as operating activities in the Consolidated Statement of
Cash Flows.

      The objective of the revenue hedging program is to reduce the potential
for longer-term unfavorable changes in foreign exchange to decrease the U.S.
dollar value of future cash flows derived from foreign currency denominated
sales. To achieve this objective, the Company will partially hedge forecasted
sales that are expected to occur over its planning cycle, typically no more than
three years into the future. The Company will layer in hedges over time,
increasing the portion of sales hedged as it gets closer to the expected date of
the transaction. The portion of sales hedged is based on assessments of
cost-benefit profiles that consider natural offsetting exposures, revenue and
exchange rate volatilities and correlations, and the cost of hedging
instruments. The Company manages its forecasted transaction exposure principally
with purchased local currency put options. On the forecasted transactions
hedged, these option contracts effectively reduce the potential for a
strengthening U.S. dollar to decrease the future U.S. dollar cash flows derived
from foreign currency denominated sales. Purchased local currency put options
provide the Company with a right, but not an obligation, to sell foreign
currencies in the future at a predetermined price. If the value of the U.S.
dollar weakens relative to other major currencies when the options mature, the
options would expire unexercised, enabling the Company to benefit from favorable
movements in exchange, except to the extent of premiums paid for the contracts.
While a weaker U.S. dollar would result in a net benefit, the market value of
the Company's hedges would have declined by $86.3 million and $67.0 million,
respectively, from a uniform 10% weakening of the U.S. dollar at December 31,
1998 and 1997. Over the last three years, the program has reduced the volatility
of cash flows and mitigated the loss in value of cash flows during periods of
relative strength in the U.S. dollar for the portion of revenues hedged. The
cash flows from these contracts are reported as operating activities in the
Consolidated Statement of Cash Flows.

      In addition to the balance sheet and revenue hedging programs, the Company
hedges interest rates on certain fixed and variable rate borrowing and investing
transactions. Interest rates are hedged with swap contracts that exchange the
cash flows from interest rates on the underlying financial instruments for those
derived from interest rates inherent in the contracts. For foreign currency
denominated borrowing and investing transactions, cross-currency interest rate
swap contracts are used, which, in addition to exchanging cash flows derived
from rates, exchange currencies at both inception and termination of the
contracts. On investing transactions, swap contracts allow the Company to
receive variable rate returns and limit foreign exchange risk, while on
borrowing transactions, these contracts allow the Company to borrow at more
favorable rates than otherwise attainable through direct issuance of variable
rate U.S. dollar debt. The cash flows from these contracts are reported as
operating activities in the Consolidated Statement of Cash Flows.


38  Merck & Co., Inc. 1998 Annual Report  Financial Section
<PAGE>
 
      A sensitivity analysis to measure potential changes in the market value of
the Company's investments, debt and related swaps from a change in interest
rates indicated that a one percentage point increase in interest rates at
December 31, 1998 and 1997 would have positively impacted the net aggregate
market value of these instruments by $424.8 million and $60.0 million,
respectively. A one percentage point decrease at December 31, 1998 and 1997
would have negatively impacted the net aggregate market value by $616.6 million
and $71.0 million, respectively. The increased impact of a change in interest
rates on the net aggregate market values at December 31, 1998 primarily results
from increased levels of longer-term fixed rate debt.

Recently Issued Accounting Standards

In June 1998, the Financial Accounting Standards Board issued Statement No. 133,
Accounting for Derivative Instruments and Hedging Activities, which requires
adoption by fiscal 2000. The Statement establishes accounting and reporting
standards requiring that every derivative instrument be recorded in the balance
sheet as either an asset or liability measured at fair value and that changes in
fair value be recognized currently in earnings, unless specific hedge accounting
criteria are met. The timing of adoption of the Statement and effect on the
Company's financial position or results of operations have not yet been
determined.

Cautionary Factors That May Affect Future Results 

This annual report and other written reports and oral statements made from time
to time by the Company may contain so-called "forward-looking statements," all
of which are subject to risks and uncertainties. One can identify these
forward-looking statements by their use of words such as "expects," "plans,"
"will," "estimates," "forecasts," "projects" and other words of similar meaning.
One can also identify them by the fact that they do not relate strictly to
historical or current facts. These statements are likely to address the
Company's growth strategy, financial results, product approvals and development
programs. One must carefully consider any such statement and should understand
that many factors could cause actual results to differ from the Company's
forward-looking statements. These factors include inaccurate assumptions and a
broad variety of other risks and uncertainties, including some that are known
and some that are not. No forward-looking statement can be guaranteed and actual
future results may vary materially.

      The Company does not assume the obligation to update any forward-looking
statement. One should carefully evaluate such statements in light of factors
described in the Company's filings with the Securities and Exchange Commission,
especially on Forms 10-K, 10-Q and 8-K (if any). In Item 1 of the Company's
annual report on Form 10-K for the year ended December 31, 1998, which will be
filed in March 1999, the Company discusses in more detail various important
factors that could cause actual results to differ from expected or historic
results. The Company notes these factors for investors as permitted by the
Private Securities Litigation Reform Act of 1995. Prior to the filing of the
Form 10-K for the year ended December 31, 1998, reference should be made to Item
1 of the Company's annual report on Form 10-K for the year ended December 31,
1997. One should understand that it is not possible to predict or identify all
such factors. Consequently, the reader should not consider any such list to be a
complete statement of all potential risks or uncertainties.

Condensed Interim Financial Data
- --------------------------------------------------------------------------------
($ in millions except
per share amounts)                    4th Q       3rd Q       2nd Q       1st Q
- --------------------------------------------------------------------------------
1998
- --------------------------------------------------------------------------------
Sales ..........................   $7,530.7    $6,838.3    $6,470.4    $6,058.8
Materials and production
  costs ........................    3,762.3     3,544.1     3,383.4     3,235.6
Marketing/administrative
  expenses .....................    1,370.2     1,087.2     1,058.8       995.1
Research/development
  expenses .....................      541.2       450.4       441.0       388.5
Acquired research ..............         --     1,039.5          --          --
Equity income from
  affiliates ...................     (176.6)     (210.5)     (271.1)     (226.1)
Gains on sales of
  businesses ...................         --    (2,147.7)         --          --
Other (income)
  expense, net .................       77.1       360.0        32.2        30.5
Income before taxes ............    1,956.5     2,715.3     1,826.1     1,635.2
Net income .....................    1,400.7     1,367.0     1,316.1     1,164.4
Basic earnings per
  common share .................       $.60        $.57        $.55        $.49
Earnings per common
  share assuming dilution ......       $.58        $.56        $.54        $.47
- --------------------------------------------------------------------------------
1997
- --------------------------------------------------------------------------------
Sales ..........................   $6,232.0    $5,927.7    $5,909.2    $5,567.9
Materials and production
  costs ........................    3,068.7     2,991.0     2,944.3     2,786.3
Marketing/administrative
  expenses .....................    1,146.0     1,048.4     1,044.2     1,060.6
Research/development
  expenses .....................      493.9       424.7       396.4       368.7
Equity income from
  affiliates ...................     (191.6)     (262.6)     (122.8)     (151.0)
Gains on sales of
  businesses ...................         --      (213.4)         --          --
Other (income)
  expense, net .................       43.2       244.7        14.8        39.9
Income before taxes ............    1,671.8     1,694.9     1,632.3     1,463.4
Net income .....................    1,242.3     1,197.2     1,154.4     1,020.3
Basic earnings per
  common share .................       $.52        $.50        $.48        $.42
Earnings per common
  share assuming dilution ......       $.51        $.48        $.47        $.41
================================================================================

      In the chart above, amounts for the third and fourth quarters of 1998 were
affected by the restructuring of the ownership and operations of AMI and the
sale of the Company's one-half interest in DMPC. Amounts for the third and
fourth quarters of 1997 were affected by the formation of the animal health
joint venture and the sale of the crop protection business.

Dividends Paid per Common Share
- --------------------------------------------------------------------------------
                         Year     4th Q     3rd Q      2nd Q      1st Q
- --------------------------------------------------------------------------------
1998..............    $.94 1/2   $.27      $.22 1/2   $.22 1/2   $.22 1/2
1997..............     .84 1/2    .22 1/2   .21        .21        .20
================================================================================

Common Stock Market Prices
- --------------------------------------------------------------------------------
1998                           4th Q        3rd Q      2nd Q       1st Q
- --------------------------------------------------------------------------------
High.......................   $80 7/8     $69 9/16    $67 1/8    $66 13/32
Low........................    60 13/16    57 1/2      55 3/4     50 11/16
- --------------------------------------------------------------------------------
1997
- --------------------------------------------------------------------------------
High.......................   $53 15/16   $54 3/32    $52 13/32  $49 15/16
Low........................    42 1/2      45 3/8      40 3/16    39
================================================================================

      The principal market for trading of the common stock is the New York Stock
Exchange under the symbol MRK.


                     Merck & Co., Inc. 1998 Annual Report  Financial Section  39
<PAGE>
 
- --------------------------------------------------------------------------------
Consolidated Statement of Income
- --------------------------------------------------------------------------------
Merck & Co., Inc. and Subsidiaries

<TABLE>
<CAPTION>
Years Ended December 31
($ in millions except per share amounts)                      1998         1997         1996
- --------------------------------------------------------------------------------------------
<S>                                                     <C>          <C>          <C>       
Sales ................................................  $ 26,898.2   $ 23,636.9   $ 19,828.7
- --------------------------------------------------------------------------------------------
Costs, Expenses and Other
Materials and production .............................    13,925.4     11,790.3      9,319.2
Marketing and administrative .........................     4,511.4      4,299.2      3,841.3
Research and development .............................     1,821.1      1,683.7      1,487.3
Acquired research ....................................     1,039.5           --           --
Equity income from affiliates ........................      (884.3)      (727.9)      (600.7)
Gains on sales of businesses .........................    (2,147.7)      (213.4)          --
Other (income) expense, net ..........................       499.7        342.7        240.8
- --------------------------------------------------------------------------------------------
                                                          18,765.1     17,174.6     14,287.9
- --------------------------------------------------------------------------------------------
Income Before Taxes ..................................     8,133.1      6,462.3      5,540.8
Taxes on Income ......................................     2,884.9      1,848.2      1,659.5
- --------------------------------------------------------------------------------------------
Net Income ...........................................  $  5,248.2   $  4,614.1   $  3,881.3
============================================================================================
Basic Earnings per Common Share ......................       $2.21        $1.92        $1.60
============================================================================================
Earnings per Common Share Assuming Dilution ..........       $2.15        $1.87        $1.56
============================================================================================
</TABLE>

- --------------------------------------------------------------------------------
Consolidated Statement of Retained Earnings
- --------------------------------------------------------------------------------
Merck & Co., Inc. and Subsidiaries

<TABLE>
<CAPTION>
Years Ended December 31
($ in millions)                                               1998         1997         1996
- --------------------------------------------------------------------------------------------
<S>                                                     <C>          <C>          <C>       
Balance, January 1 ...................................  $ 17,291.5   $ 14,772.2   $ 12,684.3
- --------------------------------------------------------------------------------------------
Net Income ...........................................     5,248.2      4,614.1      3,881.3
Common Stock Dividends Declared ......................    (2,353.0)    (2,094.8)    (1,793.4)
- --------------------------------------------------------------------------------------------
Balance, December 31 .................................  $ 20,186.7   $ 17,291.5   $ 14,772.2
============================================================================================
</TABLE>

- --------------------------------------------------------------------------------
Consolidated Statement of Comprehensive Income
- --------------------------------------------------------------------------------
Merck & Co., Inc. and Subsidiaries

<TABLE>
<CAPTION>
Years Ended December 31
($ in millions)                                               1998         1997         1996
- --------------------------------------------------------------------------------------------
<S>                                                     <C>          <C>          <C>       
Net Income ...........................................  $  5,248.2   $  4,614.1   $  3,881.3
- --------------------------------------------------------------------------------------------
Other Comprehensive Loss
Net unrealized loss on investments,
   net of tax and net income realization .............        (5.6)       (17.6)       (10.8)
Minimum pension liability, net of tax ................       (24.7)       (12.4)        (6.5)
- --------------------------------------------------------------------------------------------
                                                             (30.3)       (30.0)       (17.3)
- --------------------------------------------------------------------------------------------
Comprehensive Income .................................  $  5,217.9   $  4,584.1   $  3,864.0
============================================================================================
</TABLE>

The accompanying notes are an integral part of these consolidated financial
statements.


40  Merck & Co., Inc. 1998 Annual Report Financial Section
<PAGE>
 
- --------------------------------------------------------------------------------
Consolidated Balance Sheet
- --------------------------------------------------------------------------------
Merck & Co., Inc. and Subsidiaries

<TABLE>
<CAPTION>
December 31
($ in millions)                                                       1998        1997
- --------------------------------------------------------------------------------------
<S>                                                              <C>         <C>      
Assets
- --------------------------------------------------------------------------------------
Current Assets
Cash and cash equivalents .....................................  $ 2,606.2   $ 1,125.1
Short-term investments ........................................      749.5     1,184.2
Accounts receivable ...........................................    3,374.1     2,876.7
Inventories ...................................................    2,623.9     2,145.1
Prepaid expenses and taxes ....................................      874.8       881.9
- --------------------------------------------------------------------------------------
Total current assets ..........................................   10,228.5     8,213.0
- --------------------------------------------------------------------------------------
Investments ...................................................    3,607.7     2,533.4
- --------------------------------------------------------------------------------------
Property, Plant and Equipment (at cost)
Land ..........................................................      228.8       216.4
Buildings .....................................................    3,664.0     3,257.8
Machinery, equipment and office furnishings ...................    6,211.7     5,388.6
Construction in progress ......................................    1,782.1     1,169.8
- --------------------------------------------------------------------------------------
                                                                  11,886.6    10,032.6
Less allowance for depreciation ...............................    4,042.8     3,423.2
- --------------------------------------------------------------------------------------
                                                                   7,843.8     6,609.4
- --------------------------------------------------------------------------------------
Goodwill and Other Intangibles (net of accumulated amortization
  of $1,123.9 million in 1998 and $815.8 million in 1997) .....    8,287.2     6,780.5
- --------------------------------------------------------------------------------------
Other Assets ..................................................    1,886.2     1,599.6
- --------------------------------------------------------------------------------------
                                                                 $31,853.4   $25,735.9
======================================================================================
Liabilities and Stockholders' Equity
- --------------------------------------------------------------------------------------
Current Liabilities
Accounts payable and accrued liabilities ......................  $ 3,682.1   $ 3,268.9
Loans payable and current portion of long-term debt ...........      624.2       902.5
Income taxes payable ..........................................    1,125.1       859.6
Dividends payable .............................................      637.4       537.6
- --------------------------------------------------------------------------------------
Total current liabilities .....................................    6,068.8     5,568.6
- --------------------------------------------------------------------------------------
Long-Term Debt ................................................    3,220.8     1,346.5
- --------------------------------------------------------------------------------------
Deferred Income Taxes and Noncurrent Liabilities ..............    6,057.0     5,060.1
- --------------------------------------------------------------------------------------
Minority Interests ............................................    3,705.0     1,166.1
- --------------------------------------------------------------------------------------
Stockholders' Equity
Common stock, one cent par value
  Authorized - 5,400,000,000 shares
  Issued - 2,967,851,980 shares ...............................       29.7        29.7
Other paid-in capital .........................................    5,614.5     5,224.3
Retained earnings .............................................   20,186.7    17,291.5
Accumulated other comprehensive (loss) income .................      (21.3)        9.0
- --------------------------------------------------------------------------------------
                                                                  25,809.6    22,554.5
Less treasury stock, at cost
  607,399,428 shares - 1998
  580,555,052 shares - 1997 ...................................   13,007.8     9,959.9
- --------------------------------------------------------------------------------------
Total stockholders' equity ....................................   12,801.8    12,594.6
- --------------------------------------------------------------------------------------
                                                                 $31,853.4   $25,735.9
======================================================================================
</TABLE>

The accompanying notes are an integral part of this consolidated financial
statement.


                     Merck & Co., Inc. 1998 Annual Report  Financial Section  41
<PAGE>
 
- --------------------------------------------------------------------------------
Consolidated Statement of Cash Flows
- --------------------------------------------------------------------------------
Merck & Co., Inc. and Subsidiaries

<TABLE>
<CAPTION>
Years Ended December 31
($ in millions)                                                            1998        1997        1996
- -------------------------------------------------------------------------------------------------------
<S>                                                                   <C>         <C>         <C>      
Cash Flows from Operating Activities
Income before taxes ................................................  $ 8,133.1   $ 6,462.3   $ 5,540.8
Adjustments to reconcile income before taxes to cash
  provided from operations before taxes:
   Acquired research ...............................................    1,039.5          --          --
   Gains on sales of businesses ....................................   (2,147.7)     (213.4)         --
   Depreciation and amortization ...................................    1,015.1       837.1       730.9
   Other ...........................................................      156.6       528.4       175.1
   Net changes in assets and liabilities:
     Accounts receivable ...........................................     (579.1)     (271.7)     (224.7)
     Inventories ...................................................     (409.5)      (53.5)     (267.6)
     Accounts payable and accrued liabilities ......................      250.1       321.8       414.2
     Noncurrent liabilities ........................................      (13.0)      (29.4)      116.8
     Other .........................................................        9.8        29.9        36.6
- -------------------------------------------------------------------------------------------------------
Cash Provided by Operating Activities Before Taxes .................    7,454.9     7,611.5     6,522.1
Income Taxes Paid ..................................................   (2,126.6)   (1,294.9)   (1,094.4)
- -------------------------------------------------------------------------------------------------------
Net Cash Provided by Operating Activities ..........................    5,328.3     6,316.6     5,427.7
- -------------------------------------------------------------------------------------------------------
Cash Flows from Investing Activities
Capital expenditures ...............................................   (1,973.4)   (1,448.8)   (1,196.7)
Purchase of securities, subsidiaries and other investments .........  (29,675.4)  (22,986.7)  (15,719.1)
Proceeds from sale of securities, subsidiaries and other 
  investments ......................................................   28,618.9    22,075.4    15,079.2
Proceeds from sales of businesses ..................................    2,586.2       910.0          --
Other ..............................................................      432.3      (152.6)     (142.7)
- -------------------------------------------------------------------------------------------------------
Net Cash Used by Investing Activities ..............................      (11.4)   (1,602.7)   (1,979.3)
- -------------------------------------------------------------------------------------------------------
Cash Flows from Financing Activities
Net change in short-term borrowings ................................     (457.2)      431.3        (7.1)
Proceeds from issuance of debt .....................................    2,379.5       653.1       327.5
Payments on debt ...................................................     (340.6)     (590.0)     (341.7)
Redemption of preferred stock of subsidiary ........................         --    (1,000.0)         --
Purchase of treasury stock .........................................   (3,625.5)   (2,572.8)   (2,493.3)
Dividends paid to stockholders .....................................   (2,253.1)   (2,039.9)   (1,728.9)
Proceeds from exercise of stock options ............................      490.1       413.3       442.2
Other ..............................................................     (114.1)     (153.9)      (36.0)
- -------------------------------------------------------------------------------------------------------
Net Cash Used by Financing Activities ..............................   (3,920.9)   (4,858.9)   (3,837.3)
- -------------------------------------------------------------------------------------------------------
Effect of Exchange Rate Changes on Cash and Cash Equivalents .......       85.1       (82.3)     (106.1)
- -------------------------------------------------------------------------------------------------------
Net Increase (Decrease) in Cash and Cash Equivalents ...............    1,481.1      (227.3)     (495.0)
Cash and Cash Equivalents at Beginning of Year .....................    1,125.1     1,352.4     1,847.4
- -------------------------------------------------------------------------------------------------------
Cash and Cash Equivalents at End of Year ...........................  $ 2,606.2   $ 1,125.1   $ 1,352.4
=======================================================================================================
</TABLE>

The accompanying notes are an integral part of this consolidated financial
statement.


42  Merck & Co., Inc. 1998 Annual Report Financial Section
<PAGE>
 
Notes to Consolidated
Financial Statements
- --------------------------------------------------------------------------------
Merck & Co., Inc. and Subsidiaries
($ in millions except per share amounts)

1. Nature of Operations

Merck is a global research-driven pharmaceutical company that discovers,
develops, manufactures and markets a broad range of human and animal health
products, directly and through its joint ventures, and provides pharmaceutical
benefit services through Merck-Medco Managed Care (Merck-Medco). Human health
products include therapeutic and preventive agents, generally sold by
prescription, for the treatment of human disorders. Pharmaceutical benefit
services primarily include managed prescription drug programs and programs to
manage health and drug utilization.

      Merck sells its human health products and provides pharmaceutical benefit
services to drug wholesalers and retailers, hospitals, clinics, government
agencies, corporations, labor unions, retirement systems, insurance carriers,
managed health care providers such as health maintenance organizations and other
institutions.

2. Summary of Accounting Policies

Principles of Consolidation - The consolidated financial statements include the
accounts of the Company and all of its subsidiaries in which a controlling
interest is maintained. For those consolidated subsidiaries where Company
ownership is less than 100%, the outside stockholders' interests are shown as
Minority interests. Investments in affiliates over which the Company has
significant influence but not a controlling interest are carried on the equity
basis.

Foreign Currency Translation - The U.S. dollar is the functional currency for
the Company's foreign subsidiaries.

Cash and Cash Equivalents - Cash equivalents are comprised of certain highly
liquid investments with original maturities of less than three months.

Inventories - The majority of domestic inventories are valued at the lower of
last-in, first-out (LIFO) cost or market. Remaining inventories are valued at
the lower of first-in, first-out (FIFO) cost or market.

Depreciation - Depreciation is provided over the estimated useful lives of the
assets, principally using the straight-line method. For tax purposes,
accelerated methods are used.

Goodwill and Other Intangibles - Goodwill of $4.3 billion in 1998 and $3.6
billion in 1997 (net of accumulated amortization) represents the excess of
acquisition costs over the fair value of net assets of businesses purchased and
is amortized on a straight-line basis over periods up to 40 years. Other
acquired intangibles principally include customer relationships of $2.7 billion
in 1998 and $2.8 billion in 1997 (net of accumulated amortization) that arose in
connection with the acquisition of Medco Containment Services, Inc. (renamed
Merck-Medco Managed Care) and patent rights approximating $.9 billion in 1998
(net of accumulated amortization) acquired as part of the restructuring of Astra
Merck Inc. (AMI). (See Note 4.) These acquired intangibles are recorded at cost
and are amortized on a straight-line basis over their estimated useful lives of
up to 40 years. The Company reviews goodwill and other intangibles to assess
recoverability from future operations using undiscounted cash flows. Impairments
are recognized in operating results to the extent that carrying value exceeds
fair value.

Stock-Based Compensation - Stock-based compensation is recognized using the
intrinsic value method. For disclosure purposes, pro forma net income and
earnings per share impacts are provided as if the fair value method had been
applied.

Use of Estimates - The consolidated financial statements are prepared in
conformity with generally accepted accounting principles and, accordingly,
include amounts that are based on management's best estimates and judgments.

Reclassifications - Certain reclassifications have been made to prior year
amounts to conform with current year presentation.

3. Divestitures

On July 1, 1998, the Company sold its one-half interest in The DuPont Merck
Pharmaceutical Company (DMPC), its joint venture with E.I. du Pont de Nemours
and Company (DuPont), to DuPont for $2.6 billion in cash, resulting in a pretax
gain of $2.15 billion ($1.25 billion after tax). The joint venture was not
significant to the Company's financial position or results of operations. This
gain was substantially offset on an after-tax basis by a $1.04 billion pretax
and after-tax charge for acquired research (see Note 4) and $338.6 million of
pretax other non recurring charges ($193.1 million after tax) included in Other
(income) expense, net. (See Note 14.)

      In July 1997, the Company sold its crop protection business for $910.0
million to Novartis, resulting in a pretax gain of $213.4 million, after taking
into account deferred income related to long-term contractual commitments
entered into in connection with the sale of the business. This business was not
significant to the Company's financial position or results of operations. This
gain was substantially offset by $207.3 million of pretax nonrecurring charges
included in Other (income) expense, net. (See Note 14.)

4. Joint Ventures

In 1982, Merck entered into an agreement with Astra AB (Astra) to develop and
market Astra's products under a royalty-bearing license. In 1993, the Company's
total sales of Astra products reached a level that triggered the first step in
the establishment of a joint venture business carried on by AMI, in which Merck
and Astra each owned a 50% share. This joint venture, formed in 1994, developed
and marketed most of Astra's new prescription medicines in the United States.
Joint venture sales were $1.7 billion for the first six months of 1998, $2.3
billion for 1997, and $1.8 billion for 1996, consisting primarily of Prilosec,
the first of a class of medications known as proton pump inhibitors, which slows
the production of acid from the cells of the stomach lining.


                     Merck & Co., Inc. 1998 Annual Report  Financial Section  43
<PAGE>
 
      On July 1, 1998, the Company and Astra completed the restructuring of the
ownership and operations of the joint venture whereby the Company acquired
Astra's interest in AMI, renamed KBI Inc. (KBI), for consideration totaling $3.1
billion, including approximately $700.0 million in cash and assumption of a $2.4
billion preferred stock obligation to Astra, which is included in Minority
interests in the consolidated financial statements. KBI's net operating assets,
excluding certain product rights, were then combined with the net assets of
Astra's wholly owned subsidiary, Astra USA, Inc., to form a new U.S. limited
partnership named Astra Pharmaceuticals, L.P. (APLP), in which Merck maintains a
limited partner interest. For a franchise fee payment of $230.0 million, which
is being amortized into income over 10 years on a straight-line basis, APLP
became the exclusive distributor of the products for which KBI retained rights.
Merck earns certain partnership returns as well as ongoing revenue based on
sales of current and future KBI products. The partnership returns include a
priority return, a fixed return and certain variable returns which are based, in
part, upon sales of certain former Astra USA, Inc. products. The fixed return
represents accretion of the carrying value of Merck's limited partnership
interest from its initial carrying value up to its liquidating net worth, which
is being recognized into income over 10 years on a straight-line basis. For a
payment of $443.0 million, which has been deferred, Astra purchased an option to
buy Merck's interest in the KBI products in 2008, 2012 or 2016, excluding
Merck's interest in the gastrointestinal medicines Prilosec and perprazole.

      In December 1998, Astra announced plans to merge with Zeneca Group Plc. If
this proposed merger is completed, Astra will be required to make one-time
payments to Merck totaling approximately $1.8 billion for the relinquishment of
certain rights, including option rights to future Astra products with no
existing or pending U.S. patents at the time of the merger. This merger would
also trigger a partial redemption of Merck's limited partnership interest in
2008. Furthermore, upon completion of the merger, Astra's option to buy Merck's
interest in the KBI products would only be exercisable in 2010 and Merck would
obtain the right to require Astra to purchase such interest in 2008.

      The Company's acquisition of Astra's interest in AMI for $3.1 billion was
accounted for under the purchase method and, accordingly, 100% of KBI's results
of operations have been included with the Company's since July 1, 1998. Pro
forma information is not provided as the impact of the transaction does not have
a material effect on the Company's results of operations for 1998 and 1997. The
purchase price was allocated based upon the fair values of the portion of assets
and liabilities acquired as determined by an independent appraisal. Purchase
price allocations resulted in the recognition of goodwill and other intangibles,
principally U.S. patent rights on in-line products, totaling $1.8 billion, to be
amortized on a straight-line basis over periods up to 20 years. The Company also
recorded a $1.04 billion charge for acquired research associated with 10 product
candidates in Phase II or later stages of development and U.S. rights to future
Astra products which have not yet entered Phase II, for which, at the
acquisition date, commercial viability had not been established. The product
candidates are in various therapeutic categories, principally gastrointestinal,
respiratory and neurological, with projected FDA approval dates in the years
1999 through 2005. None of these future products is individually material to the
Company. The fair value of the acquired research was determined based upon the
present value of each product's projected future cash flows utilizing an income
approach. The implied risk adjusted discount rate utilized averaged 26%, with a
range of 12% to 37%, depending on the applicable product's stage of completion,
as well as its probability of technical and marketing success. A cost approach
was also utilized to corroborate the values determined under the income
approach. In applying the cost approach, consideration was given to the level of
research and development expenditures within Astra, the appropriate required
rates of return within the market place and the cost of reproduction for the
acquired assets. Both of these approaches are appropriate under generally
accepted valuation methods and yielded similar results. The future products
considered in the valuation are all subject to the normal risks and
uncertainties associated with demonstrating the safety and efficacy required to
obtain timely FDA approval. Pursuant to agreements with Astra, the Company
anticipates that APLP and Astra will bear all costs to complete the development
of these products.

      In 1989, Merck formed a joint venture with Johnson & Johnson to develop
and market a broad range of nonprescription medicines for U.S. consumers. This
50% owned venture was expanded into Europe in 1993, and into Canada in 1996.
Sales of product marketed by the joint venture were $514.2 million for 1998,
$483.7 million for 1997 and $530.2 million for 1996.

      In 1991, Merck and DuPont formed an independent, research-driven,
worldwide pharmaceutical joint venture, equally owned by each party. DuPont
contributed its entire pharmaceutical and radiopharmaceutical imaging agents
businesses, and provided administrative services. Merck contributed cash and
European marketing rights to several of its prescription medicines, and provided
research and development and international industry expertise. Joint venture
sales were $686.2 million for the first six months of 1998 and $1.3 billion for
1997 and 1996, consisting primarily of cardiovascular, radiopharmaceutical and
central nervous system products. On July 1, 1998, the Company sold its one-half
interest in the joint venture to DuPont for $2.6 billion in cash. (See Note 3.)

      In 1994, Merck and Pasteur Merieux Connaught established an equally owned
joint venture to market vaccines and collaborate in the development of
combination vaccines for distribution in Europe. Joint venture vaccine sales
were $560.4 million for 1998, $581.3 million for 1997 and $663.0 million for
1996.

      In August 1997, Merck and Rhone-Poulenc combined their animal health and
poultry genetics businesses to form Merial Limited (Merial), a fully integrated,
stand-alone joint venture, equally owned by each party. Merial is the world's
largest company dedicated to the discovery, manufacture and marketing of
veterinary pharmaceuticals and vaccines. Merck contributed developmental
research personnel, sales and marketing activities, and animal health products,
as well as its poultry genetics business. Rhone-Poulenc contributed research and
development, manufacturing, sales and marketing activities, and animal health
products, as well as its poultry genetics business. The formation of Merial has
not had a material impact on comparability of net income. Merial sales were $1.8
billion for 1998 and $746.3 million for 1997. Animal health sales reported in
Merck's 1997 consolidated sales were $448.3 million prior to August 1.


44  Merck & Co., Inc. 1998 Annual Report  Financial Section
<PAGE>
 
5. Affiliates Accounted for Using the Equity Method

Investments in affiliates accounted for using the equity method are included in
Other assets and were $1.1 billion at December 31, 1998 and $693.7 million at
December 31, 1997. This increase primarily reflects the restructuring of the
Company's investment in AMI into APLP, partially offset by the sale of the
Company's one-half interest in DMPC. (See Notes 3 and 4.) Dividends and
distributions received from these affiliates were $919.3 million in 1998, $791.0
million in 1997 and $476.2 million in 1996. Summarized information for these
affiliates is as follows:

Years Ended December 31                           1998         1997         1996
- --------------------------------------------------------------------------------
Sales ...................................     $7,095.6     $5,655.8     $4,441.4
Materials and production costs ..........      2,191.1      1,349.3        959.4
Other expense, net ......................      2,757.8      1,852.9      1,725.2
Income before taxes .....................      2,146.7      2,453.6      1,756.8
================================================================================
December 31                                       1998         1997
- -------------------------------------------------------------------
Current assets...........................     $2,693.0     $2,475.9
Noncurrent assets........................      2,036.6      2,824.0
Current liabilities......................      2,280.2      1,920.1
Noncurrent liabilities...................        281.4        699.8
===================================================================

6. Financial Instruments

Foreign Currency Risk Management

The Company has established revenue and balance sheet hedging programs to
protect against reductions in value and volatility of future foreign currency
cash flows caused by changes in foreign exchange rates. The objectives and
strategies of these programs are described in the Analysis of Liquidity and
Capital Resources section of the Financial Review.

      The Company partially hedges forecasted revenues denominated in foreign
currencies with purchased currency options. When the dollar strengthens against
foreign currencies, the decline in the value of foreign currency cash flows is
partially offset by the recognition of gains in the value of purchased currency
options designated as hedges of the period. Conversely, when the dollar weakens,
the increase in the value of foreign currency cash flows is reduced only by the
recognition of the premium paid to acquire the options designated as hedges of
the period. Market value gains and premiums on these contracts are recognized in
Sales when the hedged transaction is recognized. The carrying value of purchased
currency options is reported in Prepaid expenses and taxes or Other assets.

      The Company continually reviews its portfolio of purchased options and
will adjust its portfolio to accommodate changes in exposure to forecasted
revenues. The most cost-effective means of decreasing coverage provided by
purchased options is to write options with terms identical to purchased options
that are no longer necessary. Deferred gains or losses that accumulate on
purchased options prior to writing an offsetting position will remain deferred
and are recognized when the hedged transaction occurs. Subsequent changes in the
market value of the written options and related purchased options are recorded
in earnings. Because the changes in market value of the purchased options
equally offset the written options, there is no net impact on earnings. The
carrying value of written currency options is reported in Accounts payable and
accrued liabilities or Deferred income taxes and noncurrent liabilities.

      Deferred gains and losses on currency options used to hedge forecasted
revenues amounted to $12.6 million and $45.3 million at December 31, 1998 and
$95.4 million and $5.9 million at December 31, 1997, respectively.

      The Company also hedges certain exposures to fluctuations in foreign
currency exchange rates that occur prior to conversion of foreign currency
denominated monetary assets and liabilities into U.S. dollars. Prior to
conversion to U.S. dollars, these assets and liabilities are translated at spot
rates in effect on the balance sheet date. The effects of changes in spot rates
are reported in earnings and included in Other (income) expense, net. The
Company hedges its exposure to changes in foreign exchange principally with
forward contracts. Because monetary assets and liabilities are marked to spot
and recorded in earnings, forward contracts designated as hedges of the monetary
assets and liabilities are also marked to spot with the resulting gains and
losses similarly recognized in earnings. Gains and losses on forward contracts
are included in Other (income) expense, net, and offset losses and gains on the
net monetary assets and liabilities hedged. The carrying values of forward
exchange contracts are reported in Accounts receivable, Other assets, Accounts
payable and accrued liabilities or Deferred income taxes and noncurrent
liabilities.

      At December 31, 1998 and 1997, the Company had contracts to exchange
foreign currencies, principally the Japanese yen, French franc and Deutschemark,
for U.S. dollars in the following notional amounts:

                                                           1998             1997
- --------------------------------------------------------------------------------
Purchased currency options ...................         $4,583.5         $1,462.7
Forward sale contracts .......................          1,972.3          1,500.9
Forward purchase contracts ...................            542.8            412.1
================================================================================

Interest Rate Risk Management

The Company uses interest rate swap contracts on certain borrowing and investing
transactions. Interest rate swap contracts are intended to be an integral part
of borrowing and investing transactions and, therefore, are not recognized at
fair value. Interest differentials paid or received under these contracts are
recognized as adjustments to the effective yield of the underlying financial
instruments hedged. Interest rate swap contracts would only be recognized at
fair value if the hedged relationship is terminated. Gains or losses accumulated
prior to termination of the relationship would be amortized as a yield
adjustment over the shorter of the remaining life of the contract or the
remaining period to maturity of the underlying instrument hedged. If the
contract remained outstanding after termination of the hedged relationship,
subsequent changes in market value of the contract would be recognized in
earnings. The Company does not use leveraged swaps and, in general, does not use
leverage in any of its investment activities that would put principal capital at
risk.

      In 1995, the Company entered into a five-year combined interest rate and
currency swap contract with a notional amount of $231.3 million at December 31,
1998 and $313.6 million at December 31, 1997 and, in 1997, a seven-year interest
rate and currency swap contract with a notional amount of $344.1 million at
December 31, 1998 and $334.2 million at December 31, 1997. In 1998, a portion of
the 1995 swap contract was terminated in conjunction with the sale of a portion
of the related asset with an immaterial impact on net income. These swaps
convert two different variable rate Dutch guilder investments to variable rate
U.S. dollar investments. The market values


                      Merck & Co., Inc. 1998 Annual Report Financial Section  45
<PAGE>
 
of these contracts are reported in Other assets or Deferred income taxes and
noncurrent liabilities with unrealized gains and losses recorded, net of tax, in
Accumulated other comprehensive income.

      At December 31, 1997, the Company had one variable maturity interest rate
swap contract outstanding with a notional amount of $85.0 million to convert
7.25% U.S. dollar callable debt issued in 1997 to variable rate U.S. dollar
debt. This swap contract was terminated in February 1998 in conjunction with the
retirement of the callable debt.

Fair Value of Financial Instruments

Summarized below are the carrying values and fair values of the Company's
financial instruments at December 31, 1998 and 1997. Fair values were estimated
based on market prices, where available, or dealer quotes.

                                                 1998                1997
                                          ------------------  ------------------
                                          Carrying      Fair  Carrying      Fair
                                             Value     Value     Value     Value
- --------------------------------------------------------------------------------
Assets
- --------------------------------------------------------------------------------
Cash and cash equivalents ..............  $2,606.2  $2,606.2  $1,125.1  $1,125.1
Short-term investments .................     749.5     749.5   1,184.2   1,184.2
Long-term investments ..................   3,607.7   3,604.3   2,533.4   2,531.8
Purchased currency
  options ..............................     170.2     137.5      54.6     144.1
Forward exchange contracts
  and currency swaps ...................      72.8      72.8     197.0     197.0
Interest rate swaps ....................        --        --        .1        .3
- --------------------------------------------------------------------------------
Liabilities
- --------------------------------------------------------------------------------
Loans payable and current portion of
  long-term debt .......................  $  624.2  $  654.7  $  902.5  $  900.5
Long-term debt .........................   3,220.8   3,336.5   1,346.5   1,387.0
Forward exchange contracts
  and currency swap ....................      86.1      86.1      22.0      22.0
================================================================================

      A summary of the carrying values and fair values of the Company's
investments at December 31 is as follows:

                                                 1998                1997
                                          ------------------  ------------------
                                          Carrying      Fair  Carrying      Fair
                                             Value     Value     Value     Value
- --------------------------------------------------------------------------------
Available-for-sale
  Debt securities ......................  $2,639.0  $2,639.0  $1,947.2  $1,947.2
  Equity securities ....................   1,000.6   1,000.6     887.6     887.6
Held-to-maturity securities ............     717.6     714.2     882.8     881.2
================================================================================

      A summary of gross unrealized gains and losses on the Company's
investments at December 31 is as follows:

<TABLE>
<CAPTION>
                                                 1998                    1997
                                          ------------------      ------------------
                                           Gross Unrealized        Gross Unrealized
                                          ------------------      ------------------
                                          Gains       Losses      Gains       Losses
- ------------------------------------------------------------------------------------
<S>                                      <C>          <C>        <C>          <C>    
Available-for-sale                                                       
  Debt securities ..................     $ 22.1       $(12.5)    $ 11.1       $ (2.8)
  Equity securities ................      124.1        (64.2)     111.3        (91.9)
Held-to-maturity securities ........         .6         (4.0)       2.9         (4.5)
====================================================================================
</TABLE>

      Gross unrealized gains and losses with respect to available-for-sale
investments are recorded, net of tax and minority interests, in Accumulated
other comprehensive (loss) income.

      Available-for-sale debt securities and held-to-maturity securities
maturing within one year totaled $535.5 million and $214.0 million,
respectively, at December 31, 1998. Of the remaining debt securities, $1.8
billion mature within six years.

      At December 31, 1998, $507.3 million of held-to-maturity securities
maturing within five years set off $507.3 million of 5.0% nontransferable note
obligations due by 2003 issued by the Company.

Concentrations of Credit Risk

As part of its ongoing control procedures, the Company monitors concentrations
of credit risk associated with financial institutions with which it conducts
business. Credit risk is minimal as credit exposure limits are established to
avoid a concentration with any single financial institution. The Company also
monitors the creditworthiness of its customers to which it grants credit terms
in the normal course of business. Concentrations of credit risk associated with
these trade receivables are considered minimal due to the Company's diverse
customer base. Bad debts have been minimal. The Company does not normally
require collateral or other security to support credit sales.

7. Inventories

Inventories at December 31 consisted of:

                                                            1998            1997
- --------------------------------------------------------------------------------
Finished goods .................................        $1,701.2        $1,230.6
Raw materials and work in process ..............           851.6           849.7
Supplies .......................................            71.1            64.8
- --------------------------------------------------------------------------------
Total (approximates current cost) ..............         2,623.9         2,145.1
Reduction to LIFO cost .........................              --              --
- --------------------------------------------------------------------------------
                                                        $2,623.9        $2,145.1
================================================================================

      Inventories valued under the LIFO method comprised approximately 37% and
42% of inventories at December 31, 1998 and 1997, respectively.

8. Loans Payable and Long-Term Debt

Loans payable at December 31, 1998 consisted primarily of $500.0 million of 5.8%
notes due 2037 that are subject to repayment at par at the option of the holders
beginning May 1999. Loans payable at December 31, 1997 consisted primarily of
commercial paper borrowings of $439.6 million and the current portion of
long-term debt of $345.8 million. The remainder in both years was principally
borrowings by foreign subsidiaries. The weighted average interest rate for these
borrowings was 6.6% and 6.4% at December 31, 1998 and 1997, respectively.

      Long-term debt at December 31 consisted of:

                                                          1998              1997
- --------------------------------------------------------------------------------
6.0% note due 2038 .........................          $1,380.0          $     --
6.8% euronotes due 2005 ....................             499.2             499.0
6.4% debentures due 2028 ...................             499.0                --
6.0% debentures due 2028 ...................             495.8                --
6.3% debentures due 2026 ...................             246.8             246.7
5.8% notes due 2037 ........................                --             500.0
Other ......................................             100.0             100.8
- --------------------------------------------------------------------------------
                                                      $3,220.8          $1,346.5
================================================================================


46  Merck & Co., Inc. 1998 Annual Report Financial Section
<PAGE>
 
      The note due 2038 issued to Astra is subject to repayment at par upon
certain events in which Astra acquires product rights held by KBI. If the
proposed merger between Astra and Zeneca Group Plc is completed (see Note 4 for
further information), the note would become payable in 2008.

      Other consisted primarily of pollution control, industrial revenue
financing and foreign borrowings at varying rates up to 8.6%.

      The aggregate maturities of long-term debt for each of the next five years
are as follows: 1999, $7.9 million; 2000, $9.4 million; 2001, $9.5 million;
2002, $6.8 million; 2003, $8.6 million.

9. Contingent Liabilities

The Company is involved in various claims and legal proceedings of a nature
considered normal to its business, principally product liability and
intellectual property cases. Additionally, the Company, along with numerous
other defendants, is a party in several antitrust actions brought by retail
pharmacies and consumers, alleging conspiracies in restraint of trade and
challenging pricing and/or purchasing practices, one of which has been certified
as a federal class action and a number of which have been certified as state
class actions. In 1996, the Company and several other defendants finalized an
agreement to settle the federal class action alleging conspiracy, which
represents the single largest group of retail pharmacy claims, pursuant to which
the Company paid $51.8 million. Since that time, the Company has entered into
other settlements on satisfactory terms. The Company has not engaged in any
conspiracy, and no admission of wrongdoing was made nor was included in the
final agreements. While it is not feasible to predict or determine the final
outcome of these proceedings, management does not believe that they should
result in a materially adverse effect on the Company's financial position,
results of operations or liquidity.

      The Company is also a party to a number of proceedings brought under the
Comprehensive Environmental Response, Compensation and Liability Act, commonly
known as Superfund, as well as under other federal and state statutes. While it
is not feasible to predict or determine the outcome of these proceedings,
management does not believe that they should result in a materially adverse
effect on the Company's financial position, results of operations or liquidity.
The Company is also remediating environmental contamination resulting from past
industrial activity at certain of its sites. The Company has taken an active
role in identifying and providing for these costs; and, therefore, management
does not believe that these expenditures should result in a materially adverse
effect on the Company's financial position, results of operations, liquidity or
capital resources.

10. Preferred Stock of Subsidiary Company

In connection with the restructuring of AMI (see Note 4), the Company assumed a
$2.4 billion par value preferred stock obligation with a dividend rate of 5% per
annum which is carried by KBI. The preferred stock is included in Minority
interests in the consolidated financial statements at December 31, 1998.

      In December 1995, the Company's wholly owned subsidiary, Merck Sharp &
Dohme Overseas Finance, S.A., issued $1.0 billion par value of variable rate
nonconvertible Preferred Equity Certificates (PECs). The PECs were redeemed by
the Company at par in September 1997.

11. Stockholders' Equity

On November 24, 1998, the Board of Directors approved an increase in authorized
common shares from 2.7 billion with no par value to 5.4 billion with one cent
par value, effective January 25, 1999. Amounts have been reclassified from
Common stock to Other paid-in capital to reflect the change in par value.
Additionally, the Board of Directors approved a two-for-one stock split of the
Company's common stock, effective February 17, 1999. All share and per share
amounts for current and prior periods presented in these financial statements
reflect the stock split.

      In 1998, 1997 and 1996, Other paid-in capital increased by $390.1 million,
$286.5 million and $225.0 million, respectively, principally as a result of
issuances of treasury stock for exercises of stock options.

      A summary of treasury stock transactions (shares in millions) is as
follows:

<TABLE>
<CAPTION>
                            1998                   1997                    1996
                    ------------------      ------------------      ------------------
                    Shares        Cost      Shares        Cost      Shares        Cost
- --------------------------------------------------------------------------------------
<S>                  <C>     <C>             <C>     <C>             <C>     <C>      
Balance, Jan. 1 ...  580.6   $ 9,959.9       554.0   $ 7,814.7       509.2   $ 5,747.4
Purchases .........   56.9     3,625.5        55.0     2,572.8        76.8     2,493.3
Issuances(1) ......  (30.1)     (577.6)      (28.4)     (427.6)      (32.0)     (426.0)
- --------------------------------------------------------------------------------------
Balance,
  Dec. 31 .........  607.4   $13,007.8       580.6   $ 9,959.9       554.0   $ 7,814.7
======================================================================================
</TABLE>

(1) Issued primarily under stock option plans.

      At December 31, 1998 and 1997, 10 million shares of preferred stock,
without par value, were authorized; none were issued.

12. Stock Option Plans

The Company has stock option plans under which employees and non-employee
directors may be granted options to purchase shares of Company common stock at
the fair market value at the time of the grant. Options generally vest in 5
years and expire in 10 years from the date of grant. The Company's stock option
plan for employees also provides for the granting of performance-based stock
awards.

      Summarized information relative to the Company's stock option plans
(shares in thousands) is as follows:

                                                     Number             Average
                                                    of Shares           Price(1)
- --------------------------------------------------------------------------------
Outstanding at December 31, 1995 ..............     182,842.0            $ 16.33
Granted .......................................      26,037.2              32.64
Exercised .....................................     (31,671.3)             13.96
Forfeited .....................................      (4,989.9)             18.84
Equivalent Options Assumed ....................         200.6              51.63
- --------------------------------------------------------------------------------
Outstanding at December 31, 1996 ..............     172,418.6              19.19
Granted .......................................      31,877.9              48.74
Exercised .....................................     (27,994.7)             14.77
Forfeited .....................................      (5,390.6)             24.30
- --------------------------------------------------------------------------------
Outstanding at December 31, 1997 ..............     170,911.2              25.27
Granted .......................................      34,802.8              63.43
Exercised .....................................     (29,727.4)             16.49
Forfeited .....................................      (3,645.9)             39.06
- --------------------------------------------------------------------------------
Outstanding at December 31, 1998 ..............     172,340.7            $ 34.20
================================================================================
(1) Weighted average exercise price.


                     Merck & Co., Inc. 1998 Annual Report  Financial Section  47
<PAGE>
 
      The number of shares and average price of options exercisable at December
31, 1998, 1997 and 1996 were 45.3 million shares at $17.75, 47.3 million shares
at $16.49 and 64.8 million shares at $15.50, respectively. At December 31, 1998
and 1997, 83.0 million shares and 114.4 million shares, respectively, were
available for future grants under the terms of these plans.

      Effective January 1, 1996, the Company adopted the provisions of Statement
No. 123, Accounting for Stock-Based Compensation. As permitted by the Statement,
the Company has chosen to continue to account for stock-based compensation using
the intrinsic value method. Accordingly, no compensation expense has been
recognized for its stock-based compensation plans other than for
performance-based awards, which was not significant. Had the fair value method
of accounting been applied to the Company's stock option plans, which requires
recognition of compensation cost ratably over the vesting period of the
underlying equity instruments, Net income would have been reduced by $192.4
million, or $.08 per share in 1998, $102.5 million, or $.04 per share in 1997
and $46.6 million, or $.02 per share in 1996. This pro forma impact only takes
into account options granted since January 1, 1995 and is likely to increase in
future years as additional options are granted and amortized ratably over the
vesting period. The average fair value of options granted during 1998, 1997 and
1996 was $20.13, $15.82 and $9.56, respectively. This fair value was estimated
using the Black-Scholes option-pricing model based on the weighted average
market price at grant date of $63.43 in 1998, $48.74 in 1997 and $32.64 in 1996
and the following weighted average assumptions:

Years Ended December 31                        1998          1997          1996
- --------------------------------------------------------------------------------
Dividend yield .......................          1.5%          1.7%          2.1%
Risk-free interest rate ..............          5.6%          6.4%          5.9%
Volatility ...........................           25%           24%           24%
Expected life (years) ................          6.5           6.6           6.7
================================================================================

      Summarized information about stock options outstanding and exercisable at
December 31, 1998 (shares in thousands) is as follows:

                                   Outstanding                   Exercisable
 Exercise             ----------------------------------   ---------------------
    Price                 Number     Average     Average       Number    Average
    Range              of Shares     Life(1)    Price(2)    of Shares   Price(2)
- --------------------------------------------------------------------------------
Under $15             15,156,960        6.75     $ 12.10   13,317,376    $ 11.72
$15 to 20             38,046,286        5.11       16.80   18,204,736      17.06
$20 to 25             28,737,046        5.10       21.40    9,857,762      21.64
$25 to 40             27,453,352        6.71       32.06    2,994,136      26.56
$40 to 50             26,752,622        8.17       48.46      554,248      45.85
$50 to 65             33,609,928        8.85       62.30      361,674      51.79
 Over $65              2,584,524        7.31       71.78        8,984      69.62
- --------------------------------------------------------------------------------
                     172,340,718                           45,298,916
================================================================================
(1) Weighted average contractual life remaining in years.
(2) Weighted average exercise price.

13. Pension and Other Postretirement Benefit Plans

In 1998, the Company adopted Statement No. 132, Employers' Disclosures About
Pensions and Other Postretirement Benefits (OPEB), which revises disclosures
about pension and other postretirement benefit plans. The following information
is provided in accordance with the requirements of this Statement.

      The net cost for the Company's pension plans consisted of the following
components:

Years Ended December 31                          1998         1997         1996
- --------------------------------------------------------------------------------
Service cost ............................     $ 134.8      $ 105.9      $ 104.1
Interest cost ...........................       158.7        149.4        144.2
Expected return on plan assets ..........      (199.2)      (175.5)      (155.4)
Net amortization ........................        15.0          4.7         13.7
- --------------------------------------------------------------------------------
Net pension cost ........................     $ 109.3      $  84.5      $ 106.6
================================================================================

      The net pension cost attributable to international plans included in the
above table was $58.8 million in 1998, $49.9 million in 1997 and $51.8 million
in 1996.

      The net cost of postretirement benefits other than pensions consisted of
the following components:

Years Ended December 31                          1998         1997         1996
- --------------------------------------------------------------------------------
Service cost ............................     $  33.7      $  24.7      $  25.2
Interest cost ...........................        53.6         48.2         45.7
Expected return on plan assets ..........       (64.2)       (53.5)       (46.9)
Net amortization ........................       (20.0)       (18.0)       (14.6)
- --------------------------------------------------------------------------------
Net postretirement benefit cost .........     $   3.1      $   1.4      $   9.4
================================================================================

      The cost of health care and life insurance benefits for active employees
was $183.4 million in 1998, $163.8 million in 1997 and $148.9 million in 1996.

      Summarized information about the changes in plan assets and benefit
obligation is as follows:

                                                                    Other
                                                                Postretirement
                                      Pension Benefits             Benefits
                                    --------------------    -------------------
                                        1998        1997        1998       1997
- -------------------------------------------------------------------------------
Fair value of plan assets
  at January 1 ...................  $2,349.5    $2,053.6    $  647.4   $  541.6
Actual return on plan assets .....     334.5       249.0        93.3      104.3
Company contributions ............     198.7       181.5          .1        7.2
Benefits paid from
  plan assets ....................    (166.6)     (139.1)       (5.8)      (5.7)
Other ............................       4.8         4.5          --         --
- -------------------------------------------------------------------------------
Fair value of plan assets
  at December 31 .................  $2,720.9    $2,349.5    $  735.0   $  647.4
===============================================================================
Benefit obligation
  at January 1 ...................  $2,388.7    $2,159.4    $  734.9   $  663.7
Service cost .....................     134.8       105.9        33.7       24.7
Interest cost ....................     158.7       149.4        53.6       48.2
Actuarial (gains) losses .........     258.0       125.8        98.3       44.8
Benefits paid ....................    (183.7)     (147.8)      (38.2)     (39.0)
Other ............................      29.4        (4.0)      (15.8)      (7.5)
- -------------------------------------------------------------------------------
Benefit obligation
  at December 31 .................  $2,785.9    $2,388.7    $  866.5   $  734.9
===============================================================================

      The fair value of international pension plan assets included in the above
table was $793.2 million in 1998 and $676.4 million in 1997. The pension benefit
obligation of international plans included in this table was $998.2 million in
1998 and $827.1 million in 1997.


48  Merck & Co., Inc. 1998 Annual Report  Financial Section
<PAGE>
 
      A reconciliation of the plans' funded status to the net asset (liability)
recognized at December 31 is as follows:

                                                                    Other
                                                                Postretirement
                                           Pension Benefits        Benefits
                                          -----------------   ------------------
                                             1998      1997      1998      1997
- --------------------------------------------------------------------------------
Funded status (benefit obligation
  in excess of plan assets) ............  $ (65.0)  $ (39.2)  $(131.5)  $ (87.5)
Unrecognized net loss (gain) ...........    380.6     269.1     (95.7)   (171.8)
Unrecognized plan changes ..............     78.8      60.9    (130.3)   (128.3)
Unrecognized transitional
  net asset ............................    (39.4)    (55.2)       --        --
- --------------------------------------------------------------------------------
Net asset (liability) ..................  $ 355.0   $ 235.6   $(357.5)  $(387.6)
- --------------------------------------------------------------------------------
Recognized as:
  Other assets .........................  $ 513.4   $ 387.8   $    --   $    --
  Accounts payable and
   accrued liabilities .................     (7.9)    (11.0)    (24.8)    (25.6)
  Deferred income taxes and
   noncurrent liabilities ..............   (284.3)   (217.2)   (332.7)   (362.0)
  Accumulated other compre-
   hensive loss ........................    133.8      76.0        --        --
================================================================================

      For pension plans with benefit obligations in excess of plan assets at
December 31, 1998 and 1997, the fair value of plan assets was $402.6 million and
$472.6 million, respectively, and the benefit obligation was $871.1 million and
$836.4 million, respectively. For those plans with accumulated benefit
obligations in excess of plan assets at December 31, 1998 and 1997, the fair
value of plan assets was $332.2 million and $197.3 million, respectively, and
the accumulated benefit obligation was $551.0 million and $360.8 million,
respectively.

      Assumptions used in determining U.S. plan information are as follows:

                                                                  Other
                                                              Postretirement
                                 Pension Benefits                Benefits
                             -----------------------     -----------------------
December 31                  1998      1997     1996     1998      1997     1996
- --------------------------------------------------------------------------------

Discount rate ..........     6.75%      7.0%     7.5%    6.75%      7.0%    7.5%
Expected rate of return
 on plan assets ........     10.0      10.0     10.0     10.0      10.0    10.0
Salary growth rate .....      4.5       4.5      4.5      4.5       4.5     4.5
================================================================================

      For the three years presented, international pension plan assumptions
ranged from 4.0% to 8.0% for the discount rate, 5.5% to 10.0% for the expected
rate of return on plan assets and 2.0% to 6.0% for the salary growth rate.

      The health care cost trend rate for other postretirement benefit plans was
7.5% at December 31, 1998. The rate will gradually decline to 5.0% over a 5-year
period. A one percentage point change in the health care cost trend rate would
have had the following effects:

                                                            One Percentage Point
                                                            --------------------
                                                             Increase   Decrease
- --------------------------------------------------------------------------------
Effect on total service and interest cost
  components ..........................................      $ 16.7      $(13.9)
Effect on benefit obligation ..........................       138.3      (119.2)
================================================================================

14.  Other (Income) Expense, Net

Years Ended December 31                        1998          1997          1996
- --------------------------------------------------------------------------------
Interest income ......................      $(307.7)      $(221.4)      $(205.4)
Interest expense .....................        205.6         129.5         138.6
Exchange gains .......................        (44.7)        (18.0)        (27.8)
Minority interests ...................        162.4         131.8         144.2
Amortization of goodwill
  and other intangibles ..............        264.3         197.2         196.2
Other, net ...........................        219.8         123.6          (5.0)
- --------------------------------------------------------------------------------
                                            $ 499.7       $ 342.7       $ 240.8
================================================================================

      Minority interests include third parties' share of exchange gains and
losses arising from translation of the financial statements into U.S. dollars.
Minority interests reflect dividends paid to Astra on $2.4 billion par value
preferred stock of a subsidiary beginning in July 1998 and, in 1997 and 1996,
dividends on the PECs, which were issued in December 1995 and redeemed in
September 1997. (See Note 10.)

      Increased amortization of goodwill and other intangibles in 1998 reflects
amortization of goodwill and other intangibles associated with the restructuring
of AMI in July 1998. (See Note 4.)

      In 1998, other, net, includes $338.6 million of nonrecurring charges,
primarily for environmental remediation costs and asset write-offs, principally
deferred start-up costs.

      In 1997, other, net, includes $207.3 million of nonrecurring charges
primarily for the loss on sale of assets, endowment of The Merck Company
Foundation and environmental remediation costs.

      Interest paid was $192.3 million in 1998, $130.5 million in 1997 and
$117.4 million in 1996.

15. Taxes on Income

A reconciliation between the Company's effective tax rate and the U.S. statutory
rate is as follows:

                                                              Tax Rate
                                            1998       -------------------------
                                          Amount       1998      1997      1996
- --------------------------------------------------------------------------------
U.S. statutory rate applied
  to pretax income ..................   $2,846.6       35.0%     35.0%     35.0%
Differential arising from:
  Acquired research .................      363.8        4.5        --        --
  Foreign earnings ..................      141.4        1.7       (.3)     (1.4)
  State taxes .......................      129.4        1.6       1.0        .1
  Tax exemption for Puerto
   Rico operations ..................     (133.1)      (1.6)     (1.9)     (1.9)
  Equity income from affiliates .....     (135.6)      (1.7)     (2.4)     (1.9)
  Other .............................     (327.6)      (4.0)     (2.8)       .1
- --------------------------------------------------------------------------------
                                        $2,884.9       35.5%     28.6%     30.0%
================================================================================

      The increase in the effective tax rate in 1998 primarily reflects the
nondeductibility of the charge for acquired research in connection with the
restructuring of AMI and the state tax impact of the gain on the sale of the
Company's one-half interest in DMPC.

      The differential arising from equity income from affiliates represents the
favorable impact of accounting for joint venture taxes as a reduction of equity
income, offset in part by significantly higher effective tax rates within the
joint ventures. The reduced benefit in 1998 reflects the impact of the AMI
restructuring, resulting in pretax partnership returns recorded in equity
income.


                     Merck & Co., Inc. 1998 Annual Report  Financial Section  49
<PAGE>
 
      Domestic companies contributed approximately 74% in 1998, 71% in 1997 and
73% in 1996 to consolidated pretax income.

      Taxes on income consisted of:

Years Ended December 31                      1998           1997           1996
- -------------------------------------------------------------------------------
Current provision
  Federal .........................      $1,750.5       $1,322.2       $1,106.2
  Foreign .........................         699.5          476.8          410.3
  State ...........................         264.7           90.5          (14.6)
- --------------------------------------------------------------------------------
                                          2,714.7        1,889.5        1,501.9
- --------------------------------------------------------------------------------
Deferred provision
  Federal .........................         226.2          (48.1)         136.9
  Foreign .........................         (21.0)          (6.4)         (15.4)
  State ...........................         (35.0)          13.2           36.1
- --------------------------------------------------------------------------------
                                            170.2          (41.3)         157.6
- --------------------------------------------------------------------------------
                                         $2,884.9       $1,848.2       $1,659.5
================================================================================

      Deferred income taxes at December 31 consisted of:

<TABLE>
<CAPTION>
                                             1998                        1997
                                   ------------------------    ------------------------
                                     Assets     Liabilities      Assets     Liabilities
- ---------------------------------------------------------------------------------------
<S>                                <C>             <C>         <C>             <C>     
Other intangibles ..............   $     --        $1,434.6    $     --        $1,173.4
Accelerated depreciation .......         --           606.6          --           591.2
Inventory related ..............      546.6           210.5       629.0           235.4
Investment related .............         --           210.0          --              --
Environmental related ..........      131.0              --        87.0              --
Compensation related ...........      110.6              --        91.3              --
Restructuring charge ...........      107.9              --       123.1              --
Pensions and OPEB ..............      176.9           140.1       172.7           105.5
Equity investments .............       57.8            91.7          --           173.1
Other ..........................      836.8           477.1       899.0           498.3
- ---------------------------------------------------------------------------------------
Subtotal .......................    1,967.6         3,170.6     2,002.1         2,776.9
Valuation allowance ............       (9.1)             --        (4.4)             --
- ---------------------------------------------------------------------------------------
Total deferred taxes ...........   $1,958.5        $3,170.6    $1,997.7        $2,776.9
- ---------------------------------------------------------------------------------------
Net deferred tax                                                             
  liabilities ..................                   $1,212.1                    $  779.2
- ---------------------------------------------------------------------------------------
Recognized as:                                                               
  Prepaid expenses and                                                       
   taxes .......................                   $ (666.3)                   $ (704.4)
  Other assets .................                      (48.2)                     (111.3)
  Income taxes payable .........                      163.5                       164.8
  Deferred income taxes                                                      
   and noncurrent                                                            
   liabilities .................                    1,763.1                     1,430.1
=======================================================================================
</TABLE>

      Income taxes paid in 1998, 1997 and 1996 were $2.1 billion, $1.3 billion
and $1.1 billion, respectively. The increase in 1998 primarily reflects taxes
paid on the gain on the sale of the Company's one-half interest in DMPC and on
APLP partnership returns, resulting from the AMI restructuring.

      At December 31, 1998, foreign earnings of $5.8 billion and domestic
earnings of $880.9 million have been retained indefinitely by subsidiary
companies for reinvestment. No provision is made for income taxes that would be
payable upon the distribution of such earnings, and it is not practicable to
determine the amount of the related unrecognized deferred income tax liability.
These earnings include income from manufacturing operations in Ireland, which
were tax-exempt through 1990 and are taxed at 10% thereafter. In addition, the
Company has domestic subsidiaries operating in Puerto Rico under a tax incentive
grant that expires in 2008.

      The Company's federal income tax returns have been audited through 1992.

16. Earnings per Share

The weighted average common shares used in the computations of basic earnings
per common share and earnings per common share assuming dilution (shares in
millions) are as follows:

Years Ended December 31                             1998        1997        1996
- --------------------------------------------------------------------------------
Average common shares outstanding ..........     2,378.8     2,409.0     2,427.2
Common shares issuable(1) ..................        62.3        60.5        62.4
- --------------------------------------------------------------------------------
Average common shares outstanding
  assuming dilution ........................     2,441.1     2,469.5     2,489.6
================================================================================
(1) Issuable primarily under stock option plans.

17. Comprehensive Income

Effective January 1, 1998, the Company adopted the provisions of Statement No.
130, Reporting Comprehensive Income, which modifies the financial statement
presentation of comprehensive income and its components. In accordance with this
Statement, a Consolidated Statement of Comprehensive Income is included in the
consolidated financial statements to present all changes in Stockholders' equity
in the periods presented other than changes resulting from transactions relating
to the Company's stock. Upon adoption, accumulated other comprehensive income of
$9.0 million at December 31, 1997 was reclassified from Retained earnings to a
separate component of Stockholders' equity.

      The components of Other comprehensive loss are as follows:

                                                                          After
                                                  Pretax(1)      Tax        Tax
- -------------------------------------------------------------------------------
Year Ended December 31, 1998
- -------------------------------------------------------------------------------
Net unrealized gain on investments ...........   $  20.6      $ (4.8)    $ 15.8
Net income realization .......................     (41.9)       20.5      (21.4)
- -------------------------------------------------------------------------------
Subtotal .....................................   $ (21.3)     $ 15.7     $ (5.6)
Minimum pension liability ....................     (47.2)       22.5      (24.7)
- -------------------------------------------------------------------------------
                                                 $ (68.5)     $ 38.2     $(30.3)
- -------------------------------------------------------------------------------
Year Ended December 31, 1997
- -------------------------------------------------------------------------------
Net unrealized loss on investments ...........   $ (74.6)     $ 57.0     $(17.6)
Minimum pension liability ....................     (37.8)       25.4      (12.4)
- -------------------------------------------------------------------------------
                                                 $(112.4)     $ 82.4     $(30.0)
- -------------------------------------------------------------------------------
Year Ended December 31, 1996
- -------------------------------------------------------------------------------
Net unrealized loss on investments ...........   $ (36.1)     $ 25.3     $(10.8)
Minimum pension liability ....................     (19.9)       13.4       (6.5)
- -------------------------------------------------------------------------------
                                                 $ (56.0)     $ 38.7     $(17.3)
===============================================================================
(1) Net of minority interest.

      The components of Accumulated other comprehensive (loss) income are as
follows:

December 31                                                 1998           1997
- -------------------------------------------------------------------------------
Net unrealized gain on investments ...............       $  22.3        $  27.9
Minimum pension liability ........................         (43.6)         (18.9)
- -------------------------------------------------------------------------------
                                                         $ (21.3)       $   9.0
===============================================================================


50  Merck & Co., Inc. 1998 Annual Report Financial Section
<PAGE>
 
18. Segment Reporting

In 1998, the Company adopted Statement No. 131, Disclosures about Segments of an
Enterprise and Related Information, which revises reporting and disclosure
requirements for operating segments. The following information is provided in
accordance with the requirements of this Statement.

      The Company's operations are principally managed on a products and
services basis and are comprised of two reportable segments: Merck
Pharmaceutical and Merck-Medco. Merck Pharmaceutical products consist of
therapeutic agents, sold by prescription, for the treatment of human disorders.
Merck-Medco revenues are derived from the filling and management of
prescriptions and health management programs. All Other includes non-reportable
human and animal health segments. Revenues and profits for these segments are as
follows:

                                       Merck
                                      Pharm-      Merck-         All
                                   aceutical       Medco       Other      Total
- -------------------------------------------------------------------------------
Year Ended December 31, 1998
- -------------------------------------------------------------------------------
Segment revenues ................  $12,839.9   $14,338.0   $ 2,274.4  $29,452.3
Segment profits .................    7,637.3       475.8     2,390.5   10,503.6
Included in segment profits:
  Equity income (loss)
   from affiliates ..............       12.7         (.4)      850.0      862.3
  Depreciation and amor-
   tization expenses ............     (103.6)      (91.9)      (47.6)    (243.1)
- -------------------------------------------------------------------------------
Year Ended December 31, 1997
- -------------------------------------------------------------------------------
Segment revenues ................  $12,122.2   $11,996.0   $ 1,851.8  $25,970.0
Segment profits .................    7,396.2       333.9     1,895.1    9,625.2
Included in segment profits:
  Equity income (loss)
   from affiliates ..............       15.0         (.5)      894.6      909.1
  Depreciation and amor-
   tization expenses ............      (89.0)      (74.8)      (31.5)    (195.3)
- -------------------------------------------------------------------------------
Year Ended December 31, 1996
- -------------------------------------------------------------------------------
Segment revenues ................  $10,700.1   $ 9,306.8   $ 1,797.3  $21,804.2
Segment profits .................    6,649.0       249.1     1,553.1    8,451.2
Included in segment profits:
  Equity income (loss)
   from affiliates ..............       15.5         (.5)      650.5      665.5
  Depreciation and amor-
   tization expenses ............      (85.3)      (44.1)       (9.0)    (138.4)
===============================================================================

      Segment profits are comprised of segment revenues less certain elements of
materials and production costs and operating expenses, including components of
equity income (loss) from joint ventures and depreciation and amortization
expenses. The vast majority of indirect production costs, research and
development expenses and general and administrative expenses, all predominantly
related to the Merck pharmaceutical business, as well as the cost of financing
these activities, are not included in the marketing segment profits. The vast
majority of goodwill and other intangibles amortization, as well as the cost of
financing capital employed, are not included in Merck-Medco segment profits.

      A reconciliation of total segment revenues to consolidated sales is as
follows:

Years Ended December 31                      1998           1997           1996
- -------------------------------------------------------------------------------
Segment revenues ..................     $29,452.3      $25,970.0      $21,804.2
Other revenues ....................         182.2          222.6          169.6
Adjustments .......................      (2,736.3)      (2,555.7)      (2,145.1)
- -------------------------------------------------------------------------------
                                        $26,898.2      $23,636.9      $19,828.7
===============================================================================

      Other revenues primarily represent sales related to divested products or
businesses. Adjustments represent the elimination of receipts reported as
revenues in the internal management system which are not reportable as revenues
under generally accepted accounting principles.

      Consolidated revenues by country where derived are as follows:

Years Ended December 31                      1998          1997          1996
- -------------------------------------------------------------------------------
United States ........................  $20,199.3     $16,984.9     $13,636.8
Japan ................................    1,160.6(1)    1,235.1(1)    1,316.1(1)
Other ................................    5,538.3       5,416.9       4,875.8
- -------------------------------------------------------------------------------
                                        $26,898.2     $23,636.9     $19,828.7
===============================================================================
(1) Exceeds 5% of consolidated sales.

      A reconciliation of total segment profits to consolidated income before
taxes is as follows:

Years Ended December 31                       1998           1997          1996
- -------------------------------------------------------------------------------
Segment profits .....................    $10,503.6      $ 9,625.2     $ 8,451.2
Other profits .......................         86.7          137.3         105.2
Adjustments .........................        180.5          145.6         155.4
Unallocated:
  Gains on sales of
   businesses .......................      2,147.7          213.4            --
  Interest income ...................        307.7          221.4         205.4
  Interest expense ..................       (205.6)        (129.5)       (138.6)
  Equity income (loss)
   from affiliates ..................         22.0         (181.2)        (64.8)
  Depreciation and
   amortization expenses ............       (772.0)        (641.8)       (592.5)
  Acquired research .................     (1,039.5)            --            --
  Research and development
   expenses .........................     (1,821.1)      (1,683.7)     (1,487.3)
  Other expenses, net ...............     (1,276.9)      (1,244.4)     (1,093.2)
- -------------------------------------------------------------------------------
                                         $ 8,133.1      $ 6,462.3     $ 5,540.8
===============================================================================

      Other profits primarily represent operating income related to divested
products or businesses. Adjustments represent the elimination of the effect of
double counting certain items of income and expense. Equity income (loss) from
affiliates includes taxes paid at the joint venture level and a portion of
equity income that is not reported in segment profits. Other expenses, net,
include expenses from corporate and manufacturing cost centers and other
miscellaneous income (expense), net.

      Net property, plant and equipment (PP&E) by country where located are as
follows:

December 31                             1998           1997              1996
- -------------------------------------------------------------------------------
United States ...............       $5,888.3       $5,017.9          $4,536.8
Japan .......................          388.5          365.4(2)          343.9(2)
Other .......................        1,567.0        1,226.1           1,046.0
- -------------------------------------------------------------------------------
                                    $7,843.8       $6,609.4          $5,926.7
===============================================================================
(2) Exceeds 5% of consolidated net PP&E.

      The Company does not disaggregate assets on a products and services basis
for internal management reporting and, therefore, such information is not
presented.


                      Merck & Co., Inc. 1998 Annual Report Financial Section  51
<PAGE>
 
Management's 
Report
- --------------------------------------------------------------------------------

Primary responsibility for the integrity and objectivity of the Company's
financial statements rests with management. The financial statements report on
management's stewardship of Company assets. These statements are prepared in
conformity with generally accepted accounting principles and, accordingly,
include amounts that are based on management's best estimates and judgments.
Nonfinancial information included in the Annual Report has also been prepared by
management and is consistent with the financial statements.

      To assure that financial information is reliable and assets are
safeguarded, management maintains an effective system of internal controls and
procedures, important elements of which include: careful selection, training and
development of operating and financial managers; an organization that provides
appropriate division of responsibility, and communications aimed at assuring
that Company policies and procedures are understood throughout the organization.
In establishing internal controls, management weighs the costs of such systems
against the benefits it believes such systems will provide. A staff of internal
auditors regularly monitors the adequacy and application of internal controls on
a worldwide basis.

      To insure that personnel continue to understand the system of internal
controls and procedures, and policies concerning good and prudent business
practices, the Company periodically conducts the Management's Stewardship
Program for key management and financial personnel. This program reinforces the
importance and understanding of internal controls by reviewing key corporate
policies, procedures and systems. In addition, an ethical business practices
program has been implemented to reinforce the Company's long-standing commitment
to high ethical standards in the conduct of its business.

      The independent public accountants have audited the Company's consolidated
financial statements as described in their report. Although their audits were
not designed for the purpose of forming an opinion on internal controls, the
Company's accounting systems, procedures and internal controls were subject to
testing and other auditing procedures sufficient to enable the independent
public accountants to render their opinion on the Company's financial
statements.

      The recommendations of the internal auditors and independent public
accountants are reviewed by management. Control procedures have been implemented
or revised as appropriate to respond to these recommendations. No material
control weaknesses have been brought to the attention of management. In
management's opinion, for the year ended December 31, 1998, the internal control
system was strong and accomplished the objectives discussed herein.


/s/ Raymond V. Gilmartin            /s/ Judy C. Lewent

Raymond V. Gilmartin                Judy C. Lewent
Chairman, President and             Senior Vice President and
Chief Executive Officer             Chief Financial Officer

Report of Independent
Public Accountants
- --------------------------------------------------------------------------------

To the Stockholders and
Board of Directors of Merck & Co., Inc.:

We have audited the accompanying consolidated balance sheet of Merck & Co., Inc.
(a New Jersey corporation) and subsidiaries as of December 31, 1998 and 1997,
and the related consolidated statements of income, retained earnings,
comprehensive income and cash flows for each of the three years in the period
ended December 31, 1998. These financial statements are the responsibility of
the Company's management. Our responsibility is to express an opinion on these
financial statements based on our audits.

      We conducted our audits in accordance with generally accepted auditing
standards. Those standards require that we plan and perform the audit to obtain
reasonable assurance about whether the financial statements are free of material
misstatement. An audit includes examining, on a test basis, evidence supporting
the amounts and disclosures in the financial statements. An audit also includes
assessing the accounting principles used and significant estimates made by
management, as well as evaluating the overall financial statement presentation.
We believe that our audits provide a reasonable basis for our opinion.

      In our opinion, the financial statements referred to above present fairly,
in all material respects, the financial position of Merck & Co., Inc. and
subsidiaries as of December 31, 1998 and 1997, and the results of their
operations and their cash flows for each of the three years in the period ended
December 31, 1998, in conformity with generally accepted accounting principles.


                                                         /s/ Arthur Andersen LLP

New York, New York                                       ARTHUR ANDERSEN LLP
January 26, 1999


52  Merck & Co., Inc. 1998 Annual Report  Financial Section
<PAGE>
 
Audit Committee's Report
- --------------------------------------------------------------------------------

The Audit Committee of the Board of Directors is comprised of five outside
directors. The members of the Committee are: Charles E. Exley Jr., Chairman;
Carolyne K. Davis, Ph.D.; Sir Derek Birkin; William N. Kelley, M.D.; and Samuel
O. Thier, M.D. The Committee held three meetings during 1998.

      The Audit Committee meets with the independent public accountants,
management and internal auditors to assure that all are carrying out their
respective responsibilities. The Audit Committee reviews the performance and
fees of the independent public accountants prior to recommending their
appointment, and meets with them, without management present, to discuss the
scope and results of their audit work, including the adequacy of internal
controls and the quality of financial reporting. Both the independent public
accountants and the internal auditors have full access to the Audit Committee.


                                                       /s/ Charles E. Exley Jr.

                                                       Charles E. Exley Jr.
                                                       Chairman, Audit Committee

Compensation and Benefits Committee's Report
- --------------------------------------------------------------------------------

The Compensation and Benefits Committee is comprised of five outside directors.
The members of the Committee are: H. Brewster Atwater Jr., Chairman; Lawrence A.
Bossidy; William G. Bowen, Ph.D.; Johnnetta B. Cole, Ph.D.; and Lloyd C. Elam,
M.D. The Committee held four meetings during 1998.

      The Compensation and Benefits Committee's major responsibilities include
providing for senior management succession and overseeing the Company's
compensation and benefit programs. The Committee seeks to provide rewards which
are highly leveraged to performance and clearly linked to Company and individual
results. The objective is to ensure that compensation and benefits are at levels
which enable Merck to attract and retain high-quality employees. The Committee
views stock ownership as a vehicle to align the interests of employees with
those of the stockholders. A long-term focus is essential for success in the
pharmaceutical industry and is encouraged by making a high proportion of
executive officer compensation dependent on long-term performance and on
enhancing stockholder value.


                                   /s/ H. Brewster Atwater Jr.

                                   H. Brewster Atwater Jr.
                                   Chairman, Compensation and Benefits Committee


                      Merck & Co., Inc. 1998 Annual Report Financial Section  53
<PAGE>
 
Selected Financial Data(1)
- --------------------------------------------------------------------------------
Merck & Co., Inc. and Subsidiaries

<TABLE>
<CAPTION>
($ in millions except
per share amounts)                     1998           1997           1996           1995           1994           1993    
- ----------------------------------------------------------------------------------------------------------------------
Results for Year:
<S>                              <C>            <C>            <C>            <C>            <C>            <C>           
Sales .........................  $ 26,898.2     $ 23,636.9     $ 19,828.7     $ 16,681.1     $ 14,969.8     $ 10,498.2    
Materials and production 
  costs .......................    13,925.4       11,790.3        9,319.2        7,456.3        5,962.7        2,497.6    
Marketing/administrative
  expenses ....................     4,511.4        4,299.2        3,841.3        3,297.8        3,177.5        2,913.9    
Research/development expenses..     1,821.1        1,683.7        1,487.3        1,331.4        1,230.6        1,172.8    
Acquired research .............     1,039.5             --             --             --             --             --    
Equity (income) loss
  from affiliates .............      (884.3)        (727.9)        (600.7)        (346.3)         (56.6)          26.1    
Gains on sales of businesses ..    (2,147.7)        (213.4)            --         (682.9)            --            --    
Restructuring charge ..........          --             --             --             --             --          775.0    
Gain on joint venture
  formation ...................          --             --             --             --         (492.0)            --    
Provision for joint
  venture obligation ..........          --             --             --             --          499.6             --    
Other (income) expense, net ...       499.7          342.7          240.8          827.6          232.8           10.1    
Income before taxes ...........     8,133.1        6,462.3        5,540.8        4,797.2        4,415.2        3,102.7    
Taxes on income ...............     2,884.9        1,848.2        1,659.5        1,462.0        1,418.2          936.5    
Net income ....................     5,248.2        4,614.1        3,881.3        3,335.2        2,997.0        2,166.2    
Basic earnings per
  common share(3) .............  $     2.21     $     1.92     $     1.60     $     1.35     $     1.19     $      .94    
Earnings per common share
  assuming dilution(3) ........  $     2.15     $     1.87     $     1.56     $     1.32     $     1.17     $      .93    
Dividends declared ............     2,353.0        2,094.8        1,793.4        1,578.0        1,463.1        1,239.0    
Dividends paid per
  common share(3) .............  $      .95     $      .85     $      .71     $      .62     $      .57     $      .52    
Capital expenditures ..........     1,973.4        1,448.8        1,196.7        1,005.5        1,009.3        1,012.7    
Depreciation ..................       700.0          602.4          521.7          463.3          475.6          348.4    
- ----------------------------------------------------------------------------------------------------------------------
Year-End Position:
Working capital ...............  $  4,159.7     $  2,644.4     $  2,897.4     $  3,870.2     $  2,291.4     $    541.6    
Property, plant and
  equipment (net) .............     7,843.8        6,609.4        5,926.7        5,269.1        5,296.3        4,894.6    
Total assets ..................    31,853.4       25,735.9       24,266.9       23,831.8       21,856.6       19,927.5    
Long-term debt ................     3,220.8        1,346.5        1,155.9        1,372.8        1,145.9        1,120.8    
Stockholders' equity ..........    12,801.8       12,594.6       11,964.0       11,735.7       11,139.0       10,021.7    
- ----------------------------------------------------------------------------------------------------------------------
Financial Ratios:
Net income as a % of:
  Sales .......................        19.5%          19.5%          19.6%          20.0%          20.0%          20.6%   
  Average total assets ........        18.2%          18.5%          16.1%          14.6%          14.3%          14.0%   
- ----------------------------------------------------------------------------------------------------------------------
Year-End Statistics:
Average common shares
  outstanding (millions)(3) ...     2,378.8        2,409.0        2,427.2        2,472.3        2,514.3        2,313.0    
Average common shares
  outstanding assuming dilution
  (millions)(3) ...............     2,441.1        2,469.5        2,489.6        2,527.3        2,557.7        2,332.0    
Number of stockholders
  of record ...................     269,600        263,900        247,300        243,000        244,700        231,300    
Number of employees ...........      57,300         53,800         49,100         45,200         47,500         47,100(4) 
==========================================================================================================================
</TABLE>

<TABLE>                         
<CAPTION>                       
($ in millions except           
per share amounts)                      1992(2)          1991          1990          1989          1988  
- -------------------------------------------------------------------------------------------------------  
Results for Year:                                                                                        
<S>                               <C>              <C>           <C>           <C>           <C>         
Sales .........................   $  9,662.5       $  8,602.7    $  7,671.5    $  6,550.5    $  5,939.5  
Materials and production 
  costs .......................      2,096.1          1,934.9       1,778.1       1,550.3       1,526.1  
Marketing/administrative                                                                                 
  expenses ....................      2,963.3          2,570.3       2,388.0       2,013.4       1,880.3  
Research/development expenses..      1,111.6            987.8         854.0         750.5         668.8  
Acquired research .............           --               --            --            --            --  
Equity (income) loss                                                                                     
  from affiliates .............        (25.8)            21.1          22.4          11.5          (2.5) 
Gains on sales of businesses ..           --               --            --            --            --  
Restructuring charge ..........           --               --            --            --            --  
Gain on joint venture                                                                                    
  formation ...................           --               --            --            --            --  
Provision for joint                                                                                      
  venture obligation ..........           --               --            --            --            --  
Other (income) expense, net ...        (46.3)           (78.1)        (69.8)        (58.2)         (4.2) 
Income before taxes ...........      3,563.6          3,166.7       2,698.8       2,283.0       1,871.0  
Taxes on income ...............      1,117.0          1,045.0         917.6         787.6         664.2  
Net income ....................      2,446.6          2,121.7       1,781.2       1,495.4       1,206.8  
Basic earnings per                                                                                       
  common share(3) .............   $     1.06       $      .91    $      .76    $      .63    $      .51  
Earnings per common share                                                                                
  assuming dilution(3) ........   $     1.05       $      .91    $      .75    $      .62    $      .50  
Dividends declared ............      1,106.9            920.3         788.1         681.5         546.3  
Dividends paid per                                                                                       
  common share(3) .............   $      .46       $      .39    $      .32    $      .28    $      .22  
Capital expenditures ..........      1,066.6          1,041.5         670.8         433.0         372.7  
Depreciation ..................        290.3            242.7         231.4         206.4         189.0  
- ---------------------------------------------------------------------------------------------------------
Year-End Position:                                                                                       
Working capital ...............   $  1,241.1       $  1,496.5    $    939.2    $  1,502.5    $  1,480.3  
Property, plant and                                                                                      
  equipment (net) .............      4,271.1          3,504.5       2,721.7       2,292.5       2,070.7  
Total assets ..................     11,086.0          9,498.5       8,029.8       6,756.7       6,127.5  
Long-term debt ................        495.7            493.7         124.1         117.8         142.8  
Stockholders' equity ..........      5,002.9          4,916.2       3,834.4       3,520.6       2,855.8  
- ---------------------------------------------------------------------------------------------------------
Financial Ratios:                                                                                        
Net income as a % of:                                                                                    
  Sales .......................         25.3%            24.7%         23.2%         22.8%         20.3% 
  Average total assets ........         24.1%            24.2%         24.1%         23.2%         20.4% 
- ---------------------------------------------------------------------------------------------------------
Year-End Statistics:                                                                                     
Average common shares                                                                                    
  outstanding (millions)(3) ...      2,307.0          2,319.8       2,344.1       2,376.6       2,373.8  
Average common shares                                                                                    
  outstanding assuming dilution                                                                          
  (millions)(3) ...............      2,330.6          2,343.3       2,363.7       2,401.6       2,398.2  
Number of stockholders                                                                                   
  of record ...................      161,200           91,100        82,300        75,600        68,500  
Number of employees ...........       38,400           37,700        36,900        34,400        32,000  
=======================================================================================================  
</TABLE>

(1)  Amounts after 1992 include the impact of the Medco acquisition on November
     18, 1993.
(2)  Results of operations for 1992 exclude the cumulative effect of accounting
     changes.
(3)  All share and per share amounts for current and prior periods reflect the
     two-for-one stock split effective February 1999. 
(4)  Increase in 1993 is due to the inclusion of 10,300 Merck-Medco employees.


54  Merck & Co., Inc. 1998 Annual Report  Financial Section

<PAGE>
 
                                                                     Exhibit 21



                         MERCK & CO., INC. SUBSIDIARIES
                                 as of 12/31/98


          Each of the subsidiaries set forth below does business under the name
stated. A subsidiary of a subsidiary is indicated by indentation under the
immediate parent.  All voting securities of the subsidiaries named are owned
directly or indirectly by the Company, except where otherwise indicated.

<TABLE> 
<CAPTION> 
                                                                        Country or State
Name                                                                    of Incorporation
- ----                                                                    ----------------
<S>                                                                     <C> 
Chibret A/S                                                                  Denmark

Hangzhou MSD Pharmaceutical Company Limited/1/                               China

International Indemnity Ltd.                                                 Bermuda

Johnson & Johnson - Merck Consumer Pharmaceuticals Company/1/                New Jersey

Laboratorios Prosalud S.A.                                                   Peru

MCM Vaccine Co./1/                                                           Pennsylvania


Merck and Company, Incorporated                                              Delaware
  Merck SH Inc.                                                              Delaware

Merck Capital Investments, Inc.                                              Delaware

Merck Capital Resources, Inc.                                                Delaware
  MSD Technology, L.P./1/                                                    Delaware
     Merck Finance Co., Inc.                                                 Delaware


Merck Liability Management Company                                           Delaware

Merck Enterprises Canada, Ltd.                                               Canada


Merck Foreign Sales Corporation Ltd.                                         Bermuda

Merck Hamilton, Inc.                                                         California

Merck Holdings, Inc.                                                         Delaware
  Chugai MSD Co., Ltd./1/  /L.L.C.                                           Japan/Delaware
  Frosst Laboratories, Inc.                                                  Delaware
  Frosst Portuguesa - Produtos Farmaceuticos, Lda.                           Portugal
  Istituto Gentili S.p.A./Inc.                                               Italy/Delaware
  KBI Inc.                                                                   Delaware
     KBI Sub Inc.                                                            Delaware
</TABLE> 
<PAGE>
 
<TABLE> 
<CAPTION> 

                                                                        Country or State
Name                                                                    of Incorporation
- ----                                                                    ----------------
<S>                                                                       <C> 
     KBI-E Inc.                                                              Delaware
     KBI-P Inc.                                                              Delaware
  Merck-Medco Holdings II Corp.                                              Delaware
     Cloverleaf International Holdings S.A.                                  Luxembourg
       Coordinated Patient Care Scandinavia AS                               Norway
          Medco Holdings S. de R.L. de C.V.                                  Mexico
            Medco de Mexico Managed Care S. de R.L. de C.V.                  Mexico
            Medco Servicios de Mexico, S. de R.L. de C.V.                    Mexico
          Medidoc AB                                                         Sweden
       Coordination Medicale et Pharmaceutique, S.A.                         France
       Fontelabor-Produtos Farmaceuticos, Lda.                               Portugal
       Merck Frosst Canada & Co.                                             Canada
          Maple Leaf Holdings SRL                                            Barbados
       Merck Sharp & Dohme (Australia) Pty. Limited                          Australia
          AMRAD Pharmaceuticals Pty. Ltd./1/                                 Australia
       Merck Sharp & Dohme B.V.                                              Netherlands
          Abello Farmacia, S.L./1/                                           Spain
          Financiere MSD S.A.S.                                              France
            MSD (Nippon Holdings) BV                                         Amsterdam
            Chibret Pharmazeutische GmbH                                     Germany
            Laboratoires Martin-Johnson & Johnson-MSD S.A.S./1/              France
            Laboratoires Merck Sharp & Dohme Chibret SNC                     France
            Pasteur Merieux MSD Gestion S.A./1/                              France
            Pasteur Merieux MSD S.N.C./1/                                    France
               Pasteur Merieux MSD A/S                                       Denmark
               Pasteur Merieux MSD GmbH                                      Germany
               Pasteur Merieux MSD Ltd. (UK)                                 Great Britain
                  Pasteur Merieux MSD Ltd. (Ireland)                         Ireland
               Pasteur Merieux MSD N.V.                                      Belgium
               Pasteur Merieux MSD S.A.                                      Spain
               Pasteur Merieux MSD S.p.A.                                    Italy
               Pasteur Vaccins S.A.                                          France
          Laboratorios Chibret, S.A.                                         Spain
          Merck Sharp & Dohme GmbH                                           Austria
          Merck Sharp & Dohme (Italia) S.p.A.                                Italy
            Abiogen Farma S.p.A.                                             Italy
            Istituto Di Richerche Di Biologia Molecolare S.p.A./1/           Italy
          MSD (Proprietary) Limited                                          South Africa
          MSD Sharp & Dohme GmbH                                             Germany
            Dieckmann Arzneimittel GmbH                                      Germany
               Woelm Pharma GmbH & Co./1/                                    Germany
            MSD Chibropharm GmbH                                             Germany
            MSD Unterstutzungskasse GmbH                                     Germany
</TABLE> 

                                       2
<PAGE>
 
<TABLE> 
<CAPTION> 
                                                                        Country or State
Name                                                                    of Incorporation
- ----                                                                    ----------------
<S>                                                                   <C> 
            Varipharm Arzneimittel GmbH                                      Germany
          Sharp & Dohme, S.A.                                                Spain
       Merck Sharp & Dohme Chibret A.G.                                      Switzerland
       Merck Sharp & Dohme (Holdings) Limited                                Great Britain
          Charles E. Frosst (U.K.) Limited                                   Great Britain
          Merck Sharp & Dohme Limited                                        Great Britain
            Johnson & Johnson.MSD Consumer Pharmaceuticals/1/                Great Britain
            Merck Sharp & Dohme Finance Europe                               Great Britain
          Thomas Morson & Son Limited                                        Great Britain
       Merck Sharp & Dohme IDEA, Inc.                                        Switzerland
       Merck Sharp & Dohme (Sweden) A.B.                                     Sweden
          Merck Sharp & Dohme (Israel - 1996) Company Ltd.                   Israel
       Merck Sharp & Dohme Trading & Service Limited Liability Company       Hungary
       MSD Ireland (Holdings) S.A.                                           Luxembourg
          Fabrica de Productos Quimicos y Farmaceuticos Abello, S.A.         Spain
          Fregenal Holdings S.A.                                             Panama
          Frosst Iberica, S.A.                                               Spain
          Laboratorios Quimico-Farmaceuticos Chibret, Lda.                   Portugal
          Merck Sharp & Dohme de Espana, S.A.                                Spain
          Merck Sharp & Dohme, Limitada                                      Portugal
          MSD Finance, B.V.                                                  Netherlands
          MSD Overseas Manufacturing Co.                                     Bermuda
            Blue Jay Investments C.V.                                        Netherlands
            Merck Sharp & Dohme (Singapore) Ltd.                             Bermuda
            MSD Ireland (Investment) Ltd.                                    Bermuda
            MSD Overseas Manufacturing Co. (Ireland)                         Ireland
               Crosswinds B.V.                                               Netherlands
               Merck Sharp & Dohme (Ireland) Ltd.                            Bermuda
               Tradewinds Manufacturing SRL                                  Barbados
          Neopharmed S.p.A.                                                  Italy
          Ruskin Limited                                                     Bermuda
       MSD (Norge) A/S                                                       Norway
       Suomen MSD Oy                                                         Finland
          Kiinteisto Oy Irmelinpesa/1/                                       Finland
          Kiinteisto Oy Viistotie 11                                         Finland
  Merck Sharp & Dohme de Venezuela, C.A.                                     Venezuela
  Merck Sharp & Dohme Holdings de Mexico, S.A. de C.V.                       Mexico
     Merck Sharp & Dohme de Mexico, S.A. de C.V.                             Mexico
  Merck Sharp & Dohme (I.A.) Corp.                                           Delaware
     Merck Sharp & Dohme (Argentina) Inc.                                    Delaware
     MSD Korea Ltd.                                                          Korea/Delaware
  Merck Sharp Dohme Ilaclari Limited Sirketi                                 Turkey
  Merck Sharp & Dohme Farmaceutica Ltda.                                     Brazil
     Prodome Quimica e Farmaceutica Ltda./1/                                 Brazil
</TABLE> 

                                       3
<PAGE>
 
<TABLE> 
<CAPTION> 
                                                                        Country or State
Name                                                                    of Incorporation
- ----                                                                    ----------------
<S>                                                                    <C> 
  Merck Sharp & Dohme (International) Limited                                Bermuda
     Merck Sharp & Dohme (Asia) Limited                                      Hong Kong
       Merck Sharp & Dohme (China) Limited                                   Hong Kong
     Merck Sharp & Dohme S.A.                                                France
  Merck Sharp & Dohme International Services B.V.                            Netherlands
  Merck Sharp & Dohme - Lebanon S.A.L.                                       Lebanon
  Merck Sharp & Dohme L.L.C.                                                 Russian Federation
  Merck Sharp & Dohme (Middle East) Limited                                  Cyprus
  Merck Sharp & Dohme of Pakistan Limited                                    Pakistan
  Merck Sharp & Dohme Quimica de Puerto Rico, Inc.                           Delaware
  Merck Sharp & Dohme S.A.R.L.                                               Morocco
  Merck Ventures, Inc.                                                       Delaware
  MSD Lakemedel (Scandinavia) Aktiebolog                                     Sweden
  Prosalud Peruana S.A.                                                      Peru
  TELERx Marketing Inc.                                                      Pennsylvania


Merck Investment Co., Inc.                                                   Delaware


Merck-Medco Managed Care, L.L.C.                                             Delaware
  CM Delaware Corporation                                                    Delaware
  DM-MG, L.L.C.                                                              Delaware
  MCCO Corp.                                                                 New Jersey
  MCCO, L.L.C.                                                               New Jersey
  Medco Containment Insurance Company of New Jersey                          New Jersey
  Medco Containment Insurance Company of New York                            New York
  Medco Containment Life Insurance Company                                   Pennsylvania
  Merck-Medco Managed Care of California, Inc.                               California
  Merck-Medco Rx Services of Florida No. 2, L.C.                             Florida
  Merck-Medco Rx Services of Florida, L.C.                                   Florida
  Merck-Medco Rx Services of Massachusetts, L.L.C.                           Massachusetts
  Merck-Medco Rx Services of Nevada, Inc.                                    Nevada
  Merck-Medco Rx Services of New Jersey, L.L.C.                              New Jersey
  Merck-Medco Rx Services of New York, L.L.C.                                New York
  Merck-Medco Rx Services of Ohio, Ltd.                                      Ohio
  Merck-Medco Rx Services of Ohio No. 2, Ltd.                                Ohio
  Merck-Medco Rx Services of Oklahoma, L.L.C.                                Oklahoma
  Merck-Medco Rx Services of Pennsylvania, L.L.C.                            Pennsylvania
  Merck-Medco Rx Services of Pennsylvania No. 2, L.L.C.                      Pennsylvania
  Merck-Medco Rx Services of Texas, L.L.C.                                   Texas
  Merck-Medco Rx Services of Virginia, L.L.C.                                Virginia
  Merck-Medco Rx Services of Washington, Inc.                                Washington
  Mergerco Delaware No. 10, L.L.C.                                           Delaware
  MW Holdings, L.L.C.                                                        Delaware
  NJRE, L.L.C.                                                               New Jersey
</TABLE> 

                                       4
<PAGE>
 
<TABLE> 
<CAPTION> 
                                                                        Country or State
Name                                                                    of Incorporation
- ----                                                                    ----------------

<S>                                                                      <C> 
  NRx Federal Corp.                                                          Delaware
  National Rx Services, Inc. of Missouri                                     Missouri
  National Rx Services No. 3, Inc. of Ohio                                   Ohio
  New York PAID Independent Practice Association, L.L.C.                     New York
  Paid Direct, Inc.                                                          Delaware
  PAID Prescriptions, L.L.C.                                                 Nevada
  Replacement Distribution Center, Inc.                                      Ohio
  The Institute for Effectiveness Research, L.L.C.                           Delaware
  Systemed, L.L.C.                                                           Delaware
     Systemed Pharmacy of Iowa, L.L.C.                                       Delaware
     Systemed Pharmacy of Ohio, Ltd.                                         Ohio

Merck Resource Management, Inc.                                              Delaware

Merck Sharp & Dohme (Europe) Inc.                                            Delaware

Merck Sharp & Dohme Industria Quimica e Veterinaria Limitada                 Brazil

Merck Sharp & Dohme (New Zealand) Limited                                    New Zealand

Merck Sharp & Dohme Overseas Finance N.V.                                    Neth. Antilles

Merck Sharp & Dohme (Panama) S.A.                                            Panama

Merck Sharp & Dohme Peru S.C.                                                Peru

Merck Sharp & Dohme (Philippines) Inc.                                       Philippines

Merial Limited/LLC/1/                                                        Great Britain/
                                                                             Delaware
  British United Turkeys Limited/1/                                          Great Britain
     Turkey Research & Development Limited/1/                                Great Britain

MSD International Holdings, Inc.                                             Delaware
  Banyu Pharmaceutical Company, Ltd./1/                                      Japan
     Banyu-A.S.C. Co., Ltd.                                                  Japan
     Nippon Merck-Banyu Co., Ltd.                                            Japan

MSD (Japan) Co., Ltd.                                                        Japan

The O'Hare Group, Inc./1/                                                    Delaware

</TABLE> 
____________
/1/ own less than 100%                      5


<PAGE>
 
                                                                      Exhibit 24


                               POWER OF ATTORNEY
                               -----------------


        Each of the undersigned does hereby appoint CELIA A. COLBERT,
MARY M. McDONALD and KENNETH C. FRAZIER and each of them, severally, his/her
true and lawful attorney or attorneys to execute on behalf of the undersigned
(whether on behalf of the Company, or as an officer or director thereof, or by
attesting the seal of the Company, or otherwise) the Form l0-K Annual Report of
Merck & Co., Inc. for the fiscal year ended December 3l, l998 under the
Securities Exchange Act of l934, including amendments thereto and all exhibits
and other documents in connection therewith.

        IN WITNESS WHEREOF, this instrument has been duly executed as of the
23rd day of February, l999.

                                      MERCK & CO., Inc.


                                      By /s/ Raymond V. Gilmartin
                                         ---------------------------------
                                        Raymond V. Gilmartin
                                        (Chairman of the Board, President
                                        and Chief Executive Officer)


/s/   Raymond V. Gilmartin        Chairman of the Board, President
- -------------------------------   and Chief Executive Officer
      Raymond V. Gilmartin        (Principal Executive Officer; Director)
                                  

/s/   Judy C. Lewent              Senior Vice President and Chief Financial
- -------------------------------   Officer (Principal Financial Officer)
      Judy C. Lewent                

/s/ Richard C. Henriques, Jr.     Vice President, Controller
- -------------------------------   (Principal Accounting Officer)
    Richard C. Henriques, Jr.    


                                   DIRECTORS


/s/ H. Brewster Atwater, Jr.            /s/  Lloyd C. Elam
- ----------------------------------      ----------------------------------
     H. Brewster Atwater, Jr.                Lloyd C. Elam

/s/ Derek Birkin                        /s/  Charles E. Exley, Jr.
- ----------------------------------      ----------------------------------
    Derek Birkin                             Charles E. Exley, Jr.


/s/ Lawrence A. Bossidy                 /s/  William N. Kelley
- ----------------------------------      ----------------------------------
    Lawrence A. Bossidy                      William N. Kelley

/s/ William G. Bowen                    /s/  Edward M. Scolnick
- ----------------------------------      ----------------------------------
    William G. Bowen                         Edward M. Scolnick

/s/ Johnnetta B. Cole                   /s/  Samuel O. Thier
- ----------------------------------      ----------------------------------
    Johnnetta B. Cole                        Samuel O. Thier

/s/ Carolyne K. Davis                    /s/ Dennis Weatherstone
- ----------------------------------       ---------------------------------
    Carolyne K. Davis                        Dennis Weatherstone
<PAGE>
 


          I, Nancy V. Van Allen, Assistant Secretary of MERCK & CO., Inc., a
Corporation duly organized and existing under the laws of the State of New
Jersey, do hereby certify that the following is a true copy of a resolution
adopted at a meeting of the Directors of said Corporation held in New York City,
New York, on February 23, l999, duly called in accordance with the provisions of
the By-Laws of said Corporation, and at which a quorum of Directors was present:


     "Special Resolution No. 5 - 1999
      -------------------------------


          RESOLVED, that the proposed form of Form l0-K Annual Report of the
     Company for the fiscal year ended December 3l, l998 presented to this
     meeting is hereby approved with such changes as the proper officers of the
     Company, with the advice of counsel, deem appropriate; and

          RESOLVED, that each officer and director who may be required to
     execute the aforesaid Form l0-K Annual Report or any amendments thereto
     (whether on behalf of the Company or as an officer or director thereof, or
     by attesting the seal of the Company, or otherwise) is hereby authorized to
     execute a power of attorney appointing Celia A. Colbert, Mary M. McDonald
     and Kenneth C. Frazier and each of them, severally, his/her true and lawful
     attorney or attorneys to execute in his/her name, place and stead (in any
     such capacity) such Form l0-K Annual Report and any and all amendments
     thereto and any and all exhibits and other documents necessary or
     incidental in connection therewith and to file the same with the Securities
     and Exchange Commission, each of said attorneys to have power to act with
     or without the others, and to have full power and authority to do and
     perform in the name and on behalf of each of said officers and directors,
     or both, as the case may be, every act whatsoever necessary or advisable to
     be done in the premises as fully and to all intents and purposes as any
     such officer or director might or could do in person."

          IN WITNESS WHEREOF, I have hereunto subscribed my signature and
affixed the seal of the Corporation this 16th day of March, l999.



 [Corporate Seal]                        /s/ Nancy V. Van Allen
                                      -------------------------------
                                             Nancy V. Van Allen
                                             Assistant Secretary

<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
CONSOLIDATED STATEMENT OF INCOME FOR THE YEAR-ENDED DECEMBER 31, 1998 AND
THE CONSOLIDATED BALANCE SHEET AS OF DECEMBER 31, 1998 AND IS QUALIFIED IN
ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000,000
        
<S>                                             <C> 
<PERIOD-TYPE>                                     12-MOS
<FISCAL-YEAR-END>                               DEC-31-1998      
<PERIOD-END>                                    DEC-31-1998      
<CASH>                                                2,606      
<SECURITIES>                                            750      
<RECEIVABLES>                                         3,374      
<ALLOWANCES>                                              0<F1>  
<INVENTORY>                                           2,624      
<CURRENT-ASSETS>                                     10,229      
<PP&E>                                               11,887      
<DEPRECIATION>                                       (4,043)     
<TOTAL-ASSETS>                                       31,853      
<CURRENT-LIABILITIES>                                 6,069      
<BONDS>                                               3,221      
                                     0      
                                               0      
<COMMON>                                                 30      
<OTHER-SE>                                           12,772      
<TOTAL-LIABILITY-AND-EQUITY>                         31,853      
<SALES>                                              26,898      
<TOTAL-REVENUES>                                     26,898      
<CGS>                                                13,925      
<TOTAL-COSTS>                                        13,925      
<OTHER-EXPENSES>                                      1,821      
<LOSS-PROVISION>                                          0<F1>  
<INTEREST-EXPENSE>                                      206      
<INCOME-PRETAX>                                       8,133      
<INCOME-TAX>                                          2,885      
<INCOME-CONTINUING>                                   5,248      
<DISCONTINUED>                                            0      
<EXTRAORDINARY>                                           0      
<CHANGES>                                                 0      
<NET-INCOME>                                          5,248      
<EPS-PRIMARY>                                          2.21      
<EPS-DILUTED>                                          2.15
<FN>
<F1> NOT MATERIAL TO THE CONSOLIDATED FINANCIAL STATEMENTS.
</FN>
         

</TABLE>

<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> 5
<LEGEND>
RESTATED FINANCIAL DATA SCHEDULE INCLUDING COLUMNS FOR THE THREE REPORTING
PERIODS ENDED MARCH 31, 1997, JUNE 30, 1997 AND SEPTEMBER 30, 1997; AND FOR
THE FISCAL YEAR ENDED DECEMBER 31, 1996.
</LEGEND>
<MULTIPLIER> 1,000,000
        
<S>                          <C>           <C>           <C>          <C> 
<PERIOD-TYPE>                       12-MOS        3-MOS         6-MOS         9-MOS
<FISCAL-YEAR-END>               DEC-31-1996  DEC-31-1997   DEC-31-1997   DEC-31-1997
<PERIOD-END>                    DEC-31-1996  MAR-31-1997   JUN-30-1997   SEP-30-1997
<CASH>                                1,352        1,737         1,587         1,282
<SECURITIES>                            829          862         1,129           885
<RECEIVABLES>                         2,656        2,722         2,697         2,966
<ALLOWANCES>                              0<F1>        0<F1>         0<F1>         0<F1>
<INVENTORY>                           2,149        2,088         2,171         2,227
<CURRENT-ASSETS>                      7,727        8,217         8,419         8,210
<PP&E>                                8,726        8,968         9,270         9,485
<DEPRECIATION>                        2,800       (2,994)       (3,134)       (3,189)
<TOTAL-ASSETS>                       24,267       24,706        25,602        25,872
<CURRENT-LIABILITIES>                 4,829        4,795         4,603         5,335
<BONDS>                               1,156        1,232         1,727         1,690
                     0            0             0             0
                               0            0             0             0
<COMMON>                                 30           30            30            30
<OTHER-SE>                           11,934       12,396        12,785        12,797
<TOTAL-LIABILITY-AND-EQUITY>         24,267       24,706        25,602        25,872
<SALES>                              19,829        5,568        11,477        17,405
<TOTAL-REVENUES>                     19,829        5,568        11,477        17,405
<CGS>                                 9,319        2,786         5,731         8,722
<TOTAL-COSTS>                         9,319        2,786         5,731         8,722
<OTHER-EXPENSES>                      1,487          369           765         1,190
<LOSS-PROVISION>                          0<F1>        0<F1>         0<F1>         0<F1>
<INTEREST-EXPENSE>                      139           25            56            90
<INCOME-PRETAX>                       5,541        1,463         3,096         4,791
<INCOME-TAX>                          1,660          443           921         1,419
<INCOME-CONTINUING>                   3,881        1,020         2,175         3,372
<DISCONTINUED>                            0            0             0             0
<EXTRAORDINARY>                           0            0             0             0
<CHANGES>                                 0            0             0             0
<NET-INCOME>                          3,881        1,020         2,175         3,372
<EPS-PRIMARY>                          1.60          .42           .90          1.40
<EPS-DILUTED>                          1.56          .41           .88          1.36
<FN>
<F1> NOT MATERIAL TO THE CONSOLIDATED FINANCIAL STATEMENTS.
</FN>
         

</TABLE>

<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> 5
<LEGEND>
RESTATED FINANCIAL DATA SCHEDULE INCLUDING COLUMNS FOR THE THREE REPORTING
PERIODS ENDED MARCH 31, 1998, JUNE 30, 1998 AND SEPTEMBER 30, 1998; AND FOR
THE FISCAL YEAR ENDED DECEMBER 31, 1997.
</LEGEND>
<MULTIPLIER> 1,000,000
       
<S>                                  <C>           <C>           <C>           <C>
<PERIOD-TYPE>                        12-MOS        3-MOS         6-MOS         9-MOS
<FISCAL-YEAR-END>               DEC-31-1997   DEC-31-1998   DEC-31-1998   DEC-31-1998
<PERIOD-END>                    DEC-31-1997   MAR-31-1998   JUN-30-1998   SEP-30-1998
<CASH>                                1,125         1,597         1,425         2,429
<SECURITIES>                          1,184         1,213         1,369         1,585
<RECEIVABLES>                         2,877         2,574         2,874         3,086
<ALLOWANCES>                              0<F1>         0<F1>         0<F1>         0<F1>
<INVENTORY>                           2,145         2,079         2,329         2,367
<CURRENT-ASSETS>                      8,213         8,387         8,897        10,333
<PP&E>                               10,033        10,329        10,726        11,208
<DEPRECIATION>                       (3,423)       (3,584)       (3,700)       (3,884)
<TOTAL-ASSETS>                       25,736        26,324        27,418        31,081
<CURRENT-LIABILITIES>                 5,569         4,879         6,000         5,797
<BONDS>                               1,347         1,845         1,344         2,726
                     0             0             0             0
                               0             0             0             0
<COMMON>                                 30            30            30            30
<OTHER-SE>                           12,565        13,097        13,615        12,512
<TOTAL-LIABILITY-AND-EQUITY>         25,736        26,324        27,418        31,081
<SALES>                              23,637         6,059        12,529        19,368
<TOTAL-REVENUES>                     23,637         6,059        12,529        19,368
<CGS>                                11,790         3,236         6,619        10,163
<TOTAL-COSTS>                        11,790         3,236         6,619        10,163
<OTHER-EXPENSES>                      1,684           389           830         1,280
<LOSS-PROVISION>                          0<F1>         0<F1>         0<F1>         0<F1>
<INTEREST-EXPENSE>                      130            39            82           139
<INCOME-PRETAX>                       6,462         1,635         3,461         6,177
<INCOME-TAX>                          1,848           471           981         2,329
<INCOME-CONTINUING>                   4,614         1,164         2,480         3,848
<DISCONTINUED>                            0             0             0             0
<EXTRAORDINARY>                           0             0             0             0
<CHANGES>                                 0             0             0             0
<NET-INCOME>                          4,614         1,164         2,480         3,848
<EPS-PRIMARY>                          1.92           .49          1.04          1.61
<EPS-DILUTED>                          1.87           .47          1.01          1.57
<FN>
<F1> NOT MATERIAL TO THE CONSOLIDATED FINANCIAL STATEMENTS.
</FN>
         


</TABLE>


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