Disclosure of one's HIV status to a potential sexual partner has important HIV prevention implications. This paper qualitatively evaluates the social and sexual contexts that influence disclosure of HIV status among methamphetamine-dependent gay men enrolled in an outpatient drug treatment research program. As part of an open-ended, semi-structured interview, 34 HIV-positive and HIV-negative men discussed how, when, to whom and under what circumstances they reveal information about their HIV status. The four factors that influence participants' decision to disclose include: (1) an HIV-negative sexual partner's disclosure; (2) sexual venue (private versus public); (3) primary versus non-primary partner; and (4) the perceived risk of the sexual act. Sexual encounters among the men in this sample often occurred in public environments with non-primary partners, and involved use of illicit substances. In these social and sexual contexts, both HIV-positive and HIV-negative participants believed that it is HIV-negative rather than HIV-positive men who should initiate safer sex dialogue and safer sex practices. Findings are helpful in crafting HIV-prevention interventions targeting substance-using gay men whose sexual practices place them at high-risk for HIV-infection.