Clinical, histological and HPV DNA hybridization findings were analyzed for 73 homosexual and 38 heterosexual men attending for anal warts; therapy results were evaluated retrospectively for 76 of these patients. Concurrent anal and penile warts occurred most commonly in the heterosexual men (p < 0.001). While perianal warts were most common in heterosexuals (p < 0.05), intraanal warts were most common in homosexuals (p < 0.001). Altogether 23 homosexual men were HIV-infected; 13 HIV-positive men followed regarding therapeutic outcome were immunologically relatively intact with mean CD4 counts of 524/mm3. Of 136 biopsy specimens 70% revealed benign hyperplasia, 27% AIN I, 2% AIN II and none AIN III. Of ISH positive samples 94% contained HPV 6/11 and 6% HPV 16/18/31/33. Anal warts were cured after an average of 2.5 (mean 1-10) therapy sessions in 64% of heterosexual, in 84% of HIV-negative homosexual and in 62% of HIV-positive homosexual men. The mean number of therapy sessions against anal warts was highest (p < 0.001) and the time for accomplishing cure for anal and penile warts was longest (p < 0.001) in the heterosexual study group.