CONTEXT: Data on the range of prescription and over-the-counter drug use in the United States are not available. OBJECTIVE: To provide recent population-based information on use of all medications, including prescription and over-the-counter drugs, vitamins and minerals, and herbal preparations/natural supplements in the United States. DESIGN, SETTING, AND PARTICIPANTS: Ongoing telephone survey of a random sample of the noninstitutionalized US population in the 48 continental states and the District of Columbia; data analyzed here were collected from February 1998 through December 1999. MAIN OUTCOME MEASURE: Use of medications, by type, during the preceding week, compared by demographic characteristics. RESULTS: Among 2590 participants aged at least 18 years, 81% used at least 1 medication in the preceding week; 50% took at least 1 prescription drug; and 7% took 5 or more. The highest overall prevalence of medication use was among women aged at least 65 years, of whom 12% took at least 10 medications and 23% took at least 5 prescription drugs. Herbals/supplements were taken by 14% of the population. Among prescription drug users, 16% also took an herbal/supplement; the rate of concurrent use was highest for fluoxetine users, at 22%. Reasons for drug use varied widely, with hypertension and headache mentioned most often (9% for each). Vitamins/minerals were frequently used for nonspecific reasons such as "health" (35%); herbals/supplements were also most commonly used for "health" (16%). CONCLUSIONS: In any given week, most US adults take at least 1 medication, and many take multiple agents. The substantial overlap between use of prescription medications and herbals/supplements raises concern about unintended interactions. Documentation of usage patterns can provide a basis for improving the safety of medication use.