Three randomized controlled trials in sub-Saharan Africa have shown that circumcision reduces the risk of acquiring HIV infection in men by approximately 60%. In this paper, we review the evidence that male circumcision protects against infection with HIV and other sexually transmitted infections (STIs) in men and their female partners. Data from the clinical trials indicate that circumcision may be protective against genital ulcer disease, Herpes simplex type 2, Trichomonas vaginalis and human papillomavirus infection in men. No evidence exists of a protective effect against Chlamydia trachomatis or Neisseria gonorrhea. There is weak evidence that circumcision has a direct protective effect on HIV infection in women, although there is likely to be an indirect benefit, since HIV prevalence is likely to be lower in circumcised male partners. Although there is little evidence from the trials of serious adverse events from the procedure and of behavioural risk compensation among circumcised men, essential operational research is being conducted to evaluate these key issues outside the trial setting as circumcision services are expanded. Following the publication of the clinical trial results in early 2007, the World Health Organization/UNAIDS has advised that promotion of male circumcision should be included as an additional HIV strategy for the prevention of heterosexually acquired HIV infection in men in areas of high HIV prevalence. As circumcision services are expanded in settings where resources are limited, non-physician providers including nurses will play an important role in the provision of services.