This review examines outcome evaluations of 127 primary drug abuse prevention programs issued between 1968 and 1977. Included were studies which measured program effects on drug use, intentions to use drugs, and/or attitudes toward drug use. The studies were gathered through an extended search, and they may represent the largest collection of prevention program outcome evaluations currently available. As part of the review process, detailed summaries of all studies were prepared. Each study was described along 70 programming and research dimensions. The descriptive data were subjected to various cross-tabular and correlational analyses. This article describes characteristics of the prevention programs, program settings and target populations, research methods, and the evaluation reports themselves. Trends over time in programming and research practices are also identified. The most important findings concern program effectiveness. Overall, the 127 programs produced only minor effects on drug use behaviors and attitudes. However, in a substudy of the ten best-researched, highest-intensity service programs, effectiveness was judged to be more substantial. The best of the available evaluations are tentatively encouraging about the efficacy of “new generation” prevention programs. The review concludes with recommendations for prevention policy making, program planning, and program evaluation.