Infections with human papillomaviruses (HPV) are common and include a diverse group of clinical syndromes involving cutaneous, genital, and respiratory epithelium. Advances in diagnostic methods, particularly DNA hybridization, have documented that HPV infection may be present in clinically normal epithelium. This “subclinical” infection appears to be more prevalent in the genital area than the appearance of overt genital warts and has been associated with failure of conventional treatment. HPV infection has also been associated with squamous cell carcinomas of the genitals, anus, and upper respiratory tract. The pathogenesis of HPV infection is incompletely understood because of the lack of a cell-culture system. HPV infection induces hyperplasia of the basal layer of the epidermis, but complete viral particles are found only in the superficial, terminally differentiated cells. Conventional therapy for HPV infection relies on physical destruction of visibly infected epithelium using a variety of modalities.