In recent years there has been a resurgence of new HIV cases in the United States among men who have sex with men (MSM). Some of these men may be at an increased risk for HIV transmission by engaging in sexual encounters at commercial or public sex venues. Indeed, researchers have consistently found reports of unprotected sex among men during venue attendance. Conceptually, there is a need to understand how the physical and social context of sex venues may influence decisions to engage in high risk behaviors while emphasizing new directions for policy-oriented research that reflect the current state of sex venue use rather than a contemporary history of public health fears and controversy. This dissertation empirically examines sexual behaviors of men who attended any of seven sex venue types during the previous month relative to HIV risk perceptions, spatial preferences for public sex encounters, perceptions of venue design, and venue-specific approaches to HIV prevention. Specifically, 204 MSM—recruited online through message discussion boards and LGBT academic e-mail listservs—completed an Internet survey. The findings suggest the potential influence of both physical (private spaces, low lighting, & condom availability) and social (non-verbal communication, perceived condom use of other venue patrons) forces on risky or safer behavior occurring at several venue types. Moreover, the results demonstrated that MSM who perceive moderate levels of behavior-specific and venue-specific HIV transmission risk still pursued risky sexual encounters during their venue attendance. This raises concern that despite some awareness of HIV risk, unprotected sex remains a health threat for those MSM who attend sex venues. In addition to these findings, two distinct frequency patterns (low and high) of Internet use to seek partners for public sex encounters were revealed through a cluster analysis. Men in the high frequency group were more likely to be HIV-positive, engage in unprotected anal-receptive intercourse, and have a preference for venues that offer opportunities to have multiple partners compared to men in the low frequency group. Knowing that some venue users initiate commercial and public sex encounters on the Internet may be useful for targeting appropriate HIV/STI interventions.