The plan of the Food and Drug Administration for implementing the evaluations and recommendations of the Drug Efficacy Study Group of the National Academy of Science—National Research Council respecting the effectiveness of drugs marketed prior to 1962 under approved new drug applications. The Drug Efficacy Study was undertaken in 1966 to evaluate all of the drugs the FDA had approved as safe prior to 1962, when Congress first required that drugs also be proved effective before marketing. The Drug Efficacy Study Group evaluated nearly 4,000 individual drug products, finding many of them ineffective or of only possible or probable effectiveness. The FDA is still in the process of implementing those judgments by removing some of the drugs from the market.