||Recent research suggests that men in primary relationships engage in condomless sex both within and outside their relationships, and a majority of human immune deficiency virus (HIV) transmission risk may actually occur within primary relationships. Sexual agreements regarding nonmonogamy among men who have sex with men (MSM) are a critical component to understanding HIV prevention in male couples. Consistent associations have been found between relationship factors and sexual agreements. Relationship power is one dyadic construct that likely shapes how sexual agreements function, but has been unexplored. Multilevel modeling was used in a cross- sectional sample of gay male couples (N=566 couples) to examine associations between demographic characteristics of partners traditionally used to define relationship power, a scale of decision-making power, and outcomes related to sexual agreements, including investment, agreement breaks, and break disclosure. Results indicated that decision- making power relative to one's partner was not associated with any agreement outcome, contrary to hypotheses. However, controlling for power, sociodemographics, including age, income, race, and HIV status, were variably associated with sexual agreements' functioning. Specifically, older partners were more invested in and less likely to break their agreements. Lower-earning partners broke their agreements more frequently, but also disclosed breaks more often. White men in interracial relationships broke their agreement more often than their partners. Concordant HIV-positive couples were less invested in their agreements and HIV-positive men disclosed breaks more frequently. HIV prevention efforts for same-sex couples must attend to the social, developmental, and cultural mechanisms that affect sexual nonmonogamy agreements among diverse, same-sex couples.