OBJECTIVE: To use existing evaluation data of community-based HIV prevention peer education workshops (PEWs) for gay men to explore the challenges in evaluating such programs in community settings. METHODS: Data came from 33 PEWs conducted with gay and bisexual men. A basic pre/post-test design was used to measure sexual health capacity. The Sexual Health Capacity Scale (SHCS) was anonymously completed before participation and twice afterward, with the men measuring perceptions of themselves before participation and perceptions of themselves after participation. The anonymous nature of the SHCS created problems for matching data so, for the most part, independent samples tests were used for analysis. RESULTS: Overall, 399 gay and bisexual men participated in PEWs. Participants perceived themselves as having more sexual health capacity after participation than before (p<0.001). Those who had previously been HIV tested before the PEW had higher perceived capacity (p<0.001). CONCLUSIONS AND IMPLICATIONS: Participation in the PEWs appeared to increase the perceived sexual health capacity of gay and bisexual male participants. Several limitations in the data arose from issues in the original data collection. A mixture of anonymous and identifiable data-sources meant that data could not always be matched to individuals. Stronger partnerships between HIV researchers and professionals within community organisations could significantly improve evaluation of the effectiveness of HIV peer education.