One-hundred-and-fifty male patients who attended the department of genitourinary medicine (GUM) completed a questionnaire which enquired into a past history of sexual assault and asked certain details about the assault and various sequelae of such an experience. Twenty-one men gave a history of sexual assault, 11 of whom had been abused before the age of 16, 7 afterwards and 3 in both age groups. Victims of such an assault were more likely to be homosexual or bisexual than heterosexual. The substantial majority i.e. 104 (81%) of the 129 patients who had not been assaulted in the past had been brought up by both natural parents. However, of the 21 males who reported a history of previous sexual abuse only 11 (52%) had been raised by both natural parents alone and 9 of the remaining 10 who divulged such information had been brought up in other circumstances. The association between not being raised entirely by both natural parents and a history of previous sexual assault was significant (P<0.01). Overall, physical contact of a sexual nature was the most commonly reported type of abuse, followed by anal and then by oral penetration. All of the perpetrators of assault were male except in one instance. Only 3 cases of assault were reported to the police or other agencies. Those who had been abused as miners were more likely to acknowledge subsequent psychological difficulties and to have obtained professional counselling. This problem is a significant one which goes largely undetected in GUM departments and elsewhere. A high index of suspicion is required if we are to offer a sympathetic and appropriate service to these victims.