SUMMARY
Barebacking (intentional unprotected anal sex) represents a significant threat to the health of gay, bisexual, and other men who have sex with men (MSM), which is not well defined and understood. Despite a relative lack of research on this issue, most MSM have heard of barebacking, and a substantial minority has had bareback sex. Individual reasons and six community-level influences that may have contributed to the emergence of barebacking are reviewed: (1) improvements in HIV treatment, (2) more complex sexual decision-making, (3) the Internet, (4) substance use, (5) safer sex fatigue, and (6) changes in HIV prevention programs. The implications of barebacking for HIV prevention are discussed, and suggestions for future research are offered.