Research investigating HIV-risk sexual behaviors of men who have sex with men usually combines gay and bisexual men, treating them as a single, homogeneous group. However, gay and bisexual men may differ in their HIV risk behavior and in psychological characteristics indicative of risk. Exclusively gay (N = 1,180) and bisexual men (N = 136) completed anonymous surveys at gay bars. The surveys assessed demographic, psychological, and behavioral data related to sexual behavior and HIV risk. Relative to exclusively gay men, bisexual men had lower intentions to use condoms in their next intercourse occasion, reported a greater frequency of oral sex with men and more oral-sex partners, knew fewer people who were HIV positive, and perceived weaker peer norms favoring safer sex and risk avoidance. One-third of bisexual men reported engaging in unprotected anal intercourse, and 17% of bisexual men had multiple unprotected anal sex partners in the past two months. Interventions tailored to the needs of bisexual men are urgently needed and should focus on increasing intentions to use condoms, increasing HIV-risk sensitization, and fostering norms favoring safer sex and risk avoidance.