In 1966, the Drug Efficacy Study of the National Research Council’s Division of Medical Sciences, which was tasked with evaluating the medical effectiveness of 3,000-4,000 drugs introduced between 1938 and 1962.

This was part of a larger initiative called the Drug Efficacy Study Implementation (DESI) program. The NAS/NRC study was requested by U.S. Food and Drug Administration (FDA) Commissioner James L. Goddard in the wake of the 1962 Kefauver-Harris Amendments to the Food, Drug, and Cosmetic Act, which mandated that all new drugs demonstrate efficacy in addition to safety before being marketed in the United States. 

Based on these reports, many drug products previously approved solely on the basis of safety were reclassified, with some found to be effective, others deemed ineffective, and some requiring further study.