Prior research has provided conflicting evidence about the association between partner awareness of an HIV-seropositive person's serostatus and HIV transmission behavior via unprotected intercourse. The current study examined partner awareness of participant HIV-seropositive status and sexual behavior in a multiethnic sample of HIV-seropositive men who have sex with men. Most HIV-seropositive men reported that their primary partners are aware, and most reported that at least some non-primary partners are aware the participant was HIV-seropositive before first having sex. Partner awareness of participant HIV-serostatus was related to unprotected sexual behavior during the past 3 months in a non-linear fashion, as men with partners who were inconsistently aware had higher rates of unprotected receptive anal intercourse than men with partners who were consistently aware or consistently unaware. Men with partners who were inconsistently aware also had higher rates of insertive oral intercourse than men with partners who were consistently aware. However, there were no differences in HIV transmission risk behavior between men with partners who were consistently aware and men with partners who were consistently unaware a participant was HIV-seropositive.