Background: Although pharmaceutical industry marketing and other factors may influence physician decisions regarding medication prescribing in the United States, little information is available about the composition of promotional efforts by promotional mode and medication class. Objectives: The aims of this study were to determine the magnitude of expenditures for common modes of promotion and to delineate patterns of promotional strategies for particular classes of medications. Methods: Nationally representative data on expenditures (in US $) for the 250 most promoted medications in the United States in 1998 were available from an independent pharmaceutical market research company for the 5 most commonly used modes of promotion. Key patterns of drug promotion were identified by descriptive statistics, a cluster analysis of expenditures by class, and an analysis of expenditure concentration. Results: In 1998, the pharmaceutical industry spent $12,724 million promoting its products in the United States, of which 85.9% was accounted for by the top 250 drugs and 51.6% by the top 50 drugs. Direct-to-consumer (DTC) advertising was more concentrated on a small subset of medications than was promotion to professionals. Overall, 1998 expenditures were dominated by free drug samples provided to physicians (equivalent retail cost of $6602 million) and office promotion ($3537 million), followed by DTC advertising ($1337 million), hospital promotion ($705 million), and advertising in medical journals ($540 million). Four distinct patterns of expenditures were observed: promotion to office physicians with little consumer promotion (14 drug classes); dual focus on office physicians and consumer advertising (4 drug classes); predominant DTC advertising (1 class: smoking-cessation products); and promotion to office- and hospital-based professionals without consumer advertising (1 class: narcotic analgesics). Conclusions: The present findings reinforce the perception that the pharmaceutical industry invests heavily in promoting its products and demonstrates that promotional expenditures are concentrated on a small number of medications. Although promotion to professionals remains dominant, DTC advertising has become key for a subset of common medications