The results of a clinical and virological survey of anal warts from 85 predominantly homosexual or bisexual men is presented, together with an improved technique for the surgical treatment of these lesions. Two types of anal warts, which were classified as either "acute" or "chronic" on the basis of their appearance and clinical behaviour, were recognized commonly. However, our laboratory investigations--which consisted of the routine histopathological examination of all specimens, together with immunohistochemical testing for the common wart antigen of specimens from 30 patients and papillomavirus typing by human papillomavirus DNA probing of 27 specimens--failed to reveal any significant differences between the two classes of anal warts. By means of a dot hybridization technique with mixed human papillomavirus DNA probes for types 6 and 11 and types 16 and 18, all wart biopsy specimens that were tested were shown to contain human papillomavirus types 6/11; two specimens also contained human papillomavirus types 16/18. Southern blot hybridization studies of eight specimens revealed that five warts contained human papillomavirus type 6 only and three warts contained human papillomavirus type 11 only. Although the surgical technique that is described was successful in terms of patient acceptance and the eventual eradication of anal warts, there was a high rate of recurrence of the lesions, which necessitated repeat operations in two-thirds of the patients. The need for counselling before surgery and for regular follow-up examinations after surgery is discussed.