This report presents descriptive information about the prevalence and quality of implementation of research-based programs from the Study of the Implementation of Research-Based Programs to Prevent Youth Substance Abuse and School Crime. The study found that, while schools reported implementing a large number of prevention programs during the 2004-05 school year, only a small proportion reported implementing programs (approximately 7.8 percent) supported by research evidence that met the methodological standards established by the study. It also estimated that less than one-half of those implementing research-based curriculum prevention programs (approximately 44.3 percent of the estimated 7.8 percent of research-based programs) met minimal standards for fidelity of implementation during the 2004-05 school year. Curriculum programs involve the provision of training or instruction to students. Results from Phase 1 indicate that they account for approximately 97 percent of the research-based prevention programs delivered in schools during the 2004-05 school year. Given the proportion of prevention programs offered in schools that are research-based, the estimated proportion of all curriculum prevention programs that are research-based and well-implemented is approximately 3.5 percent. A variety of factors are associated with the adoption and fidelity of implementation of research-based prevention programs. Main findings include: (1) Information was examined on over 300 programs that were found on existing lists of "promising" or "effective" prevention programs. The study identified 19 school-based prevention programs that demonstrated evidence of effectiveness through this systematic review of literature; (2) A survey collecting data on prevention programs in the nation's public schools found that the 19 research-based programs accounted for an estimated 7.8 percent of the programs implemented during the 2004-05 school year; and (3) Approximately 44.3 percent of the research-based curriculum programs, or just 3.5 percent of all programs implemented in schools, met minimum standards for overall fidelity of implementation based on four program-specific measures. Appended are: (1) Methodology; (2) Summary Report on the research synthesis; and (3) Efforts to Collect Data on Program Funding From School Personnel. (Contains 43 tables, 1 figure, 6 exhibits and 34 footnotes.)