We describe 99 (experimental and certain quasi-experimental) U.S.-based trials, reported or published since 1988, of behavioral and social interventions that measured prespecified behavioral and biologic outcomes and aimed to reduce risk for HIV infection. Studies identified through June 1998 by the HIV/AIDS Prevention Research Synthesis project were grouped into 4 risk behavior areas: drug-related (k [number of studies] = 48), heterosexual youth (k = 24), heterosexual adult (k = 17), and same-sex (k = 10). We compared the studies in the 4 areas by variables key to the development, evaluation, and transfer of interventions. Participants comprised injection drug users (43% of studies), drug users out of treatment (29%), African Americans (18%), clinic patients (18%), youth in schools (10%), and drug users in treatment (10%). Most studies were randomized (85%), provided another intervention to the control or comparison groups (71%), and evaluated behavioral interventions (92%). On average, interventions were conducted in 5 sessions (total, 8 hours) during 3 months. The theoretical basis of the intervention was not noted in 57% of the reports. At least one variable from each of the 3 outcome classifications was measured in 8% of the studies: behavioral, biologic, and psychosocial. Distinct profiles exist for the 4 risk areas. Addressing gaps in research and reporting would be helpful for analytical and program activities. This sizable portfolio of evaluated interventions contributes to effectiveness reviews and to considerations of transfer to program practice.