Male-on-male rapes and sexual assaults comprise fewer than 10% of such assaults reported to the police, and so many physicians seldom encounter them. This paper provides an overview of the nature of sexual assault encountered by males, ensuing injuries, and comparisons with male-on-female assault cases. The retrospective epidemiological study was on two cohorts seen at St. Mary's Sexual Assault Referral Centre, Manchester. The participants were Centre clients seen between October 1986 and mid-May 2003; 376 male eases (370 individual clients) and 7,789 female cases (7,403 individual clients). The main outcome measure was the presence of injury (abrasion, laceration, or bruise) to defined body areas. The results showed that 66% of male cases (when assault type was known) had been raped, significantly fewer than in female cases, (p 0.00, a 0.05, O.R. 0.474, 95% C.I. 0.357 to 0.63). Eighteen per cent of male cases that had a forensic medical examination presented with an anal injury, significantly more than in females (p 0.00, a 0.05, O.R. 6.101, 95% C.I. 4.216 to 8.829). Significantly fewer males than females sustained injuries to other body areas. The conclusion was that males were significantly more likely (six times) than females to receive at least one injury to the anal area. Even so, males are five times more likely to have no anal injury.