The overwhelming majority of literature which suggests circumcision is protective against HIV infection has been carried out in heterosexual individuals, and predominantly in resource-limited settings. A cross-sectional study found that uncircumcised gay American men were more likely to have prevalent HIV infection, but it was not known whether they had been infected by insertive or receptive intercourse.  

One study has explored the relationship between circumcision and HIV transmission in gay men in Sydney, Australia. Between 1993 and 1999 a total of 74 gay men were interviewed soon after being diagnosed with recent infection. The men were asked to nominate a unprotected sexual encounter with a serodiscordant or HIV status unknown partner at which they believed they became infected with HIV. When there was more than one possible high-risk event, the researcher chose the most likely occasion. Participants were also asked to report all episodes of unprotected anal intercourse in the six months before their seroconversion.

The researchers hypothesised that if the presence of a foreskin was important in HIV transmission, those men who had been infected by insertive unprotected anal intercourse would be more likely to be uncircumcised than those infected by receptive unprotected anal intercourse.

Sixty-three of the men nominated an event as their highest possible risk activity. For 11 men this was insertive unprotected anal intercourse, for 52 it was unprotected receptive intercourse. All but one of the 11 men who reported unprotected receptive intercourse as the most likely source of HIV infection reported no receptive unprotected anal intercourse in the six months before seroconversion and one reported receptive unprotected anal intercourse with a regular partner who was definitely HIV-negative.

In total 20 of the men (27%) were circumcised. There was no association between circumcision and reporting insertive unprotected anal intercourse as the highest risk practice. Of the additional eleven men who denied unprotected anal intercourse as the event which they believed had led to their HIV infection, eight also denied having had unprotected anal intercourse in the previous six months. Of these eight, three were circumcised (38%).

The researchers found that 17% of gay men with newly acquired HIV infection reported insertive unprotected anal intercourse as their highest risk sexual activity. This suggest insertive unprotected anal intercourse is an important means of HIV transmission in this population.

The researchers found no association between circumcision status and infection by insertive unprotected anal intercourse. Additionally, men who had seroconverted despite no reported event of unprotected anal intercourse were also more likely to be uncircumcised. The researchers suggested that this would imply that the foreskin is not the main source of HIV infection in gay men who become infected by insertive UAI, and that other sites such as the distal urethra, must be important in HIV acquisition.

This study is limited by its small sample and it is possible that some men who reported receptive unprotected anal intercourse as their highest risk behaviour may have been infected by insertive unprotected anal intercourse. The researchers suggested that their data showing there is no difference in the circumcision status of men infected by receptive or insertive unprotected anal intercourse suggests that circumcision is not strongly protective against HIV infection in gay men. Further larger studies, preferably of prospective design are needed to confirm the absence of a relationship between circumcision and HIV infection risk in gay men.