Human immunodeficiency virus (HIV) prevention programs are directed to persons at risk for acquiring and transmitting HIV because of their sexual behaviors or drug use. Effective HIV prevention requires monitoring risk behaviors among persons who are infected, persons who are at highest risk for infection, and the general population. The Behavioral Risk Factor Surveillance System (BRFSS) provides behavioral data at the state level. Because sexual behavior questions are not part of the BRFSS core instrument, in 1997, an optional module was developed and used by 23 states and Puerto Rico. This report summarizes the analysis of these data, which indicates that 11% of respondents had multiple sex partners and 4.2% reported other high-risk behaviors. These findings underscore the continued need for education about behaviors that place persons at risk for HIV infection, promotion of HIV testing among those who engage in these behaviors, and counseling to reduce risk.