This paper examines sexual risk-taking within a sample of sexually active gay and bisexual men entering substance abuse treatment (n = 383), and identifies correlates of unprotected anal sex within this group. Sexual risk-taking was high, with 55% of these men engaging in anal intercourse without a condom within a 90-day period. Correlates of unprotected anal sex varied somewhat when looking at unprotected anal sex with a primary partner only and with non-primary partners; substance use variables (number of drugs used, use of inhalant nitrites or stimulant drugs with sex, length of time since use of alcohol/drugs, loss of control problems associated with alcohol/drug use) appear to play more of a role in unprotected anal sex with non-primary partners. Overall, logistic regression analyses indicated that sexual risk was greater for those who were more sexually active, enjoyed unprotected anal sex with withdrawal prior to ejaculation, did not approve of sex outside of a love relationship, and identified themselves as more risky. In addition, those who reported more social problems due to substance use had fewer expectations that substance use increased risk, had been HIV-tested, and used reappraisal/problem-solving coping strategies showed greater risk with a primary partner only. Sexual risk with non-primary partners was greater for those who used more drugs, reported more difficulty avoiding high-risk sex when aroused and were HIV+. The paper discusses the implications of these findings for the design of sexual risk-reduction interventions.