We studied 173 biopsies of histologically determined Bowen's disease and looked for the presence of papillomavirus antigen using immunoperoxidase staining. Fifty-nine of the lesions were located at the head, 49 at the extremities, 36 at the trunk and 29 originated from the genital region. Papillomavirus capsid antigen could be clearly identified in 39 (22.5%) cases. Eleven (38%) of the 29 lesions located on genital skin were positive for papillomavirus capsid antigen while 28 (19.4%) of the 144 biopsies from other skin regions contained viral antigen. Our findings are suggestive of an etiologic relationship between the virus and this dermatosis which represents a special variant of squamous cell carcinoma. They indicate that human papillomaviruses may play an important role in the development of cutaneous malignancies.