This study was undertaken to assess the frequency with which gay and bisexual men in New York City engage in intentional unprotected anal sex, or "barebacking," and to examine explanations about the emergence of barebacking. A total of 518 men completed a brief intercept survey. Of the 448 men who were familiar with the term "barebacking" 204 (45.5%) reported bareback sex in the past 3 months prior to assessment. HIV seropositive men were significantly more likely than HIV seronegative men to report this behavior and reported significantly more sexual partners with which they had engaged in intentional unprotected anal intercourse. Participants reported significantly more acts of seroconcordant bareback sex (intentional unprotected anal intercourse with a partner of the same HIV status) than those of serodiscordant bareback sex. Men who reported barebacking also reported significantly more benefits associated with this behavior. The Internet and the availability of sexually oriented chat rooms, HIV treatment advances, emotional fatigue regarding HIV, and the increased popularity of "club" drugs were commonly cited as reasons for the barebacking phenomenon.