Background: This study examined venue-based networks constituted by affiliation with gay bars and street intersections where male sex workers (MSWs) congregate to find their sexual/drug-sharing partners and network influence on risky sexual behavior (e.g., unprotected anal intercourse [UAI]) and HIV infection. Methods: Data collected in 2003 to 2004 in Houston, Texas, consists of 208 MSWs affiliated with 15 gay bars and 51 street intersections. Two-mode network analysis was conducted to examine structural characteristics in affiliation networks, as well as venue-based network influence on UAI and HIV infection. Results: Centralized affiliation patterns were found where only a few venues were popular among MSWs, and these were highly interdependent. Distinctive structural patterns of venue-based clustering were associated with UAI and infection. Individuals who shared venue affiliation with MSWs who engage in UAI were less likely to have UAI themselves. This suggests a downhill effect; that is, individuals compensate for their risk of infection by adjusting their own risk-taking behavior, based on their perceptions of their venue affiliates. Conclusions: Venue-based HIV/AIDs interventions could be tailored to specific venues so as to target specific clusters that are more likely to engage in risky sexual behavior.