INTRODUCTION: There is a lack of recent data on the extent to which gay men engage in insertive anal intercourse (IAI) and receptive anal intercourse (RAI). Accurate assessments of the overall risk of infection from HIV and other sexually transmitted infections (STIs) require such data because versatile men who engage in both roles have heightened vulnerability for becoming infected and infecting others. AIM: To investigate the extent to which gay men are versatile with regard to having IAI and RAI. MAIN OUTCOME MEASURES: Percentages of gay men who reported engaging in IAI, RAI, or both during the past 12 months and in their most recent sexual encounter. METHODS: Eight hundred fifty-six Australian gay men completed an online survey to retrospectively report on their sexual practices over the past 12 months. RESULTS: Of men who had anal intercourse in the past 12 months, 83% had both IAI and RAI, of whom 57% were highly versatile in that they had approximately equal numbers of partners for IAI and RAI. Of men who had anal intercourse in their most recent sexual encounter, as many as one in five (20%) had reciprocal anal intercourse, having both IAI and RAI with the same partner in a single encounter. Condom use was significantly less likely with reciprocal (38%) than nonreciprocal anal intercourse (50%; P = 0.04). While highly versatile men were less likely to know their HIV status, practices at most recent sexual encounter such as reciprocal anal intercourse and condom use were not significantly related to either their HIV status or that of their partner. CONCLUSIONS: Engaging in both IAI and RAI appears to be common among gay men. HIV/STI prevention strategies would benefit from paying attention to the implications of high rates of versatile sexual practices, particularly the tendency for condoms to be used less often when having reciprocal anal intercourse.