Using the immunoperoxidase technique and a broadly cross-reactive antiserum which detects infection with any papillomavirus, papillomavirus capsid antigen was demonstrated in 25 of 48 cutaneous papillomas and in two of 38 cutaneous dysplasias. Both positive dysplastic lesions were diagnosed on histopathologic examination as bowenoid papulosis. Antigen-positive cutaneous warts were scattered in all age categories and at all body sites. In addition, there was little variation in antigen expression by morphologic type of wart. Antigen was localized in the nucleus of superficial epithelial cells. The amount of staining was variable, with some warts showing large numbers of stained nuclei. In other warts only isolated cells stained. In both cases of bowenoid papulosis, small foci of positively stained cells were observed. The finding of papillomavirus antigen in two of 21 cases of bowenoid papulosis is suggestive of an etiologic relationship between this lesion and a papillomavirus. An examination of antigen-negative cases of bowenoid papulosis for a papillomavirus genome will be necessary to confirm these results.