Dark rooms in Brazilian nightclubs: a matter of concern for STD/HIV policymakers.

A mixed methods study in Brazil identified patterns of drug use, violence and sexual behaviours in a representative sample of nightclubs and patrons. Ethnographic observations were performed inside the nightclubs and showed the existence of "dark rooms" - areas reserved for sexual intercourse - in nightclubs targeting men who have sex with men. The letter describes characteristics of the sexual behaviour in these areas.