Recently, an alarming trend toward unprotected anal intercourse has emerged in men who have sex with men. A highly dangerous form of unprotected anal intercourse, barebacking--the deliberate and conscious choice to engage in anal sex without condoms knowing that there are risks involved--has received much attention in the gay press. This trend poses new challenges for HIV prevention. As the target population changes, prevention interventions must also evolve to remain effective. A review of the scientific literature on risk behaviors and the popular literature and websites devoted to barebacking suggests that many contextual factors influence the decision to engage in unprotected anal intercourse. This review examines the most salient contextual factors affecting risk behavior in gay/bisexual men. It also identifies four main cohorts and predominant contextual factors that appear to motivate unprotected anal intercourse in each. In answering the question "where do we go from here," we conclude that contextual issues must be addressed in hybrid prevention interventions that include harm reduction, motivational interviewing, and traditional approaches.