The goal of this analysis was to examine whether partner status impacted behavioral outcomes from the Seropositive Urban Men's Intervention Trial (SUMIT). We contrasted sample characteristics of HIV-positive gay and bisexual men with and without main partners and then examined differences in sexual behaviors among men participating in an enhanced HIV prevention intervention compared to those in a standard condition. Logistic regression analyses were performed to differentiate characteristics of men with and without main partners and mixed-model logistic regression analyses were performed to test for intervention effects. Men with main partners showed a greater likelihood of having unprotected anal sex with any partner, although the number of male sexual partners was higher for men without a main partner. SUMIT generally produced few differences in sexual risk behaviors and did not affect several potential mediator variables of the relationship between the intervention and sexual behaviors with main and nonmain partners.