One hundred eight patients were studied who had anogenital lesions showing microscopic features as seen in bowenoid papulosis (BP), a recently described condition occurring most commonly in young adults. Patients typically show multiple papules, small nodules, or plaques that clinically mimic verrucae or nevocellular nevi. Although the lesions show microscopic cytologic atypia, a distinction from Bowen's disease, erythroplasia of Queyrat, and other forms of carcinoma in situ can usually be made on the basis of histologic and clinical criteria. The disorder responds to conservative treatment, although recurrences are not uncommon. Evolution of the lesions to invasive carcinoma was not observed. Mounting evidence links the development of BP to infection with human papilloma virus, but other viruses, as well as hormonal and immunologic factors, may also play a role.