Establishing school-based drug prevention programs was the aim of the Drug-Free Schools and Communities Act of 1986 (DFSCA). A summary of the findings of a longitudinal study of DFSCA is presented in this report. Revitalized in 1995 as the Safe and Drug-Free Schools and Communities Act (SDFSCA), the Act's scope was extended to include prevention of violence. Programs in 19 school districts were studied over four years by repeatedly surveying a cohort of students, beginning when the students were in grades five and six. The study's primary purpose was to assess whether drug prevention programs make a difference for youth; and, if so, what strategies were most successful. Findings reported under "Student Behaviors, Beliefs, and Attitudes about Drugs," include comparison of the two groups' responses over time, profiles of users and non-users, and "What Students Say About Drugs." Under "Home School, and Community Risk Indicators" are topics on school environment and violence; under "Drug Prevention Programs and Their Effects on Student Outcomes" are findings on program consistency and effectiveness, student participation, and "Outcomes of Prevention Programs." A summary of study findings, conclusions, data analyses, a discussion of implications, a bibliography, and a "Glossary of Analysis Variables" are provided. (EMK)