Objective: To assess circumcision status as a risk factor for HIV seroconversion in homosexual men. DESIGN,

Setting and participants: The Health in Men (HIM) study was a prospective cohort of homosexual men in Sydney, Australia. HIV–negative men (n = 1426) were recruited primarily from community–based sources between 2001 and 2004 and followed to mid–2007. Participants underwent annual HIV testing, and detailed information on sexual risk behaviour was collected every 6 months.

Main outcome measure: HIV incidence in circumcised compared with uncircumcised participants, stratified by whether or not men predominantly practised the insertive role in anal intercourse.

Results: There were 53 HIV seroconversions during follow–up; an incidence of 0.78 per 100 person–years. On multivariate analysis controlling for behavioural risk factors, being circumcised was associated with a nonsignificant reduction in risk of HIV seroconversion [hazard ratio 0.78, 95% confidence interval (CI) 0.42–1.45, P = 0.424]. Among one–third of study participants who reported a preference for the insertive role in anal intercourse, being circumcised was associated with a significant reduction in HIV incidence after controlling for age and unprotected anal intercourse (UAI) (hazard ratio 0.11, 95% CI 0.03–0.80, P = 0.041). Those who reported a preference for the insertive role overwhelmingly practised insertive rather than receptive UAI.

Conclusions: Overall, circumcision did not significantly reduce the risk of HIV infection in the HIM cohort. However, it was associated with a significant reduction in HIV incidence among those participants who reported a preference for the insertive role in anal intercourse. Circumcision may have a role as an HIV prevention intervention in this subset of homosexual men.