HIV prevention educators frequently encourage gay and bisexual men (GBM) to negotiate condom use prior to sexual engagement. Identifying groups of GBM based on their presexual agreements can aid efforts to tailor interventions. Using cross-sectional data from 1,188 GBM who reported having sex with a nonprimary sex partner in the 90 days prior to the survey, the authors identified presexual agreement patterns. For both HIV-positive and HIV-negative GBM, two groups existed: men agreeing to no anal sex and men agreeing to anal sex with condoms. Among HIV-negative participants, there was a group agreeing to anal sex without specifying condom use. Among HIV-positive participants, there was a group agreeing to anal sex without condoms; this was the largest group of HIV-positive participants. Despite a presexual agreement to use condoms, substance use during sex increased the risk of unprotected anal sex. Suggestions for applying harm reduction to HIV prevention based on agreement classifications are discussed. (Contains 5 tables.)