Prevalence studies of sexual molestation in men attending genitourinary medicine (GUM) clinics have concentrated on experiences in adulthood or as a child, or on men who report male sexual partners only. Use of questionnaires in such studies can lead to under-reporting of 'sensitive' events. Our aim is to identify the lifetime prevalence of sexual molestation in men attending a GUM clinic using a self-administered, computerized interview via a cross-sectional survey. Eighteen per cent of respondents reported sexual molestation as an adult and 12% reported child sexual abuse (CSA). Sexual molestation in adulthood was more common in men who reported male sexual partners and in men reporting child sexual abuse. Fourteen per cent of victims reported being infected with a sexually transmitted infection (STI) after adult sexual molestation. In conclusion, a significant proportion of men attending GUM services report sexual molestation. Further research is required into effective ways of addressing this unmet need.