In 1996, the Centers for Disease Control and Prevention (CDC), in collaboration with many partners, initiated the HIV/AIDS Prevention Research Synthesis (PRS) project to accumulate HIV prevention research studies and analyze their effectiveness in reducing sexual and drug-related risk behaviors for HIV transmission. The PRS team developed standardized guidelines and procedures for the systematic reviews, conducted systematic searches for pertinent studies, characterized the selected studies, analyzed effectiveness data, and established a cumulative database. As of June 1998, the database contained more than 5000 reports: 4068 were reports that met the PRS scope criteria for inclusion and 586 of those reports contained outcome data from an intervention study. Of the 586 reports that included outcome data, 276 have been reviewed: 223 (81%) included measures of PRS-specified behavioral or biologic HIV-related outcomes, and 124 of the 223 (56%) used PRS-defined rigorous study designs. The PRS database is a valuable resource for accessing and integrating the literature on HIV prevention research. CDC is committed to 1) updating the database; 2) producing systematic reviews, including meta-analyses, related to key research questions; and 3) disseminating findings to encourage and facilitate the use of science-based research in preventing HIV infection.