Virological studies were performed on 12 patients with epidermodysplasia verruciformis (EV). Three types of lesions were observed: red plaques, pityriasis versicolor (PV)-like macules and plane warts. Human papillomavirus (HPV) 14, 20 and 21 were isolated from the plaques, HPV 3, 14 and 38 from flat warts and HPV 5, 12, 17, 20 and 38 from PV-like lesions. No clear relationship could be established between the different lesions and the types of HPV. Types 17 and 20 have been isolated most frequently from Japanese EV patients and HPV 5, frequently detected in other countries, is less common, whereas HPV 8 has not been isolated. Skin cancers occurred in six of the cases (50%) and all had benign lesions that were PV-like. At least one type of HPV 5, 17 or 20 could be isolated from these benign lesions and HPV 17 or 20 detected in the cancers. These three types of HPV in EV patients appear to be involved in the malignant transformation.