This study, the first random household probability sample of unmarried adults in an HIV epicenter, examined the prevalence and correlates of HIV risk behaviors among sexually active unmarried heterosexual white and black adults (n = 848) in San Francisco, California. Racial or gender differences were found in the HIV risk factors among the men and women in our sample. More whites (17% men, 15% women) than blacks (12% men, 5% women) reported they had ever used injection drugs. White women were more likely to report that they had a sexual partner who used injection drugs (17%) than white men (11%), black women (5%), or black men (4%). Also, men were more likely than women to have had two or more sexual partners in the past year without using condoms: 43% of white men compared to 34% of white women and 40% of black men compared to 24% of black women. Among all ethnic and gender groups, more than half of those at sexual risk for HIV infection reported never using condoms. Of those at risk, more black women (75%) than white women (53%) reported they never used condoms with their sexual partners within the past year. However, only slightly more black men (62%) than white men (60%) at sexual risk for HIV reported they never used condoms with their sexual partners during the past year. High levels of HIV risk behaviors were associated with low income, not having a primary sexual partner, less enjoyment of condoms, and greater barriers to using condoms. The results support the need for major intervention programs and social marketing campaigns to promote the use of condoms by enhancing enjoyment of and reducing barriers to condom use, especially among sexual partners of black women.