Three decades into the HIV/AIDS epidemic, there is a resurgence of HIV among men who have sex with men (MSM). This trend is mirrored by an increase in sexual risk behaviors, such as barebacking. The term generally refers to intentional unprotected anal intercourse with men of unknown or seropositive antibodystatus. Unfortunately, barebacking is an understudied and largely ignored HIV risk behavior among MSM. This study heeds researchers' call to examine the phenomenon by providing an indicator of the extent of barebacking among MSM Internet users, determining sociodemographic characteristics of men engaging in barebacking, and identifying psychosocial and behavioral factors associated with barebacking. To this end, MSM Internet users were recruited online and completed a web-based survey (N = 240). Findings show that 40% of MSM in this geographically diverse sample reported engaging in the behavior. Results of univariate and multivariate analyses show that a complex combination of factors underlies barebacking. Psychosocial characteristics of MSM low perception of benefits to avoid HIV risk behavior, high perception of barriers to avoid HIV risk, low self-efficacy for limiting HIV risk, and high sexual sensation seeking are significantly related to barebacking. Compared to non-barebackers, men who engage in bareback sex are also more likely to practice unprotected anal intercourse, be drunk on alcohol in sexual contexts, and use the Internet to meet sex partners. Additionally, cultural elements that exist outside of the individual influence MSM's barebacking behavior. Compared to non-barebackers, men who bareback report a low perception of safer sex social norms. Findings in this study show there is not one salient operative dynamic that explains barebacking. Rather, factors associated with barebacking form a sex-centric confluence of psychosocial, experiential, as well as structural and technological influences that exist outside of the individual. These factors suggest opportunities for reducing the rate of HIV transmission among MSM, and men who bareback in particular, through proactive and ecological intervention approaches that encourage community empowerment and collective responsibilities for safer sex.