Venue-based HIV prevention interventions, especially in sex on premise venues, can disrupt high-risk sexual networks. However, prior to intervening, it is essential to understand the person-venue dynamics that contribute to HIV risk. As such, we conducted five ethnographic observations at each of six venues where alcohol is sold and sex occurs onsite (2 each porn theaters, sex clubs, and dance clubs) frequented by gay and other men who have sex with men (G&MSM) in the Buenos Aires metropolitan area. Alcohol use, sexual behavior, and person-venue dynamics differed markedly across venue types. In dance clubs, substantial alcohol consumption often preceded visits to the darkroom for sex which, at times, included unprotected anal and vaginal intercourse. Condoms, although available, were not easily accessible. HIV prevention messaging was generally non-existent. These venues are in critical need of interventions to reduce HIV transmission risk.