Human papillomaviruses (HPVs) found in lesions of 11 patients suffering from epidermodysplasia verruciformis were compared to HPV type 1 (HPV-1) and HPV type 2 (HPV-2) previously characterized in plantar and common warts, respectively. Complementary RNAs (cRNAs) to HPV-1, HPV-2, and viruses obtained from two patients with epidermodysplasia verruciformis (J.D. HPV and J.K. HPV) were used in cRNA.DNA filter hybridization experiments. No sequence homology was detected between HPV-1 or HPV-2 DNAs and DNAs obtained from the 11 epidermodysplasia verruciformis HPV isolates. Furthermore, with J.D. and J.K. HPV cRNAs, epidermodysplasia verruciformis HPV DNAs fell into two groups showing little, if any, sequence homology. A lower extent of annealing was observed for the DNAs of some isolates showing a genetic heterogeneity within each of the two groups. Almost no antigenic crossreaction was detected by immunodiffusion and indirect immunofluorescence tests, either between epidermodysplasia verruciformis HPVs and HPV-1 or HPV-2 or between J.D. and J.K. HPVs. Viruses belonging to the same group have common antigenic properties, but antigenic differences were observed when two of the viruses sharing only partial DNA sequence homology were compared. Viruses related to J.D. HPV were preferentially associated with flat wart-like lesions of epidermodysplasia verruciformis and were further found in the lesions of five patients bearing multiple flat warts. Viruses related to J.K. HPV were found in morphologically distinct lesions (red spots) present in some patients with epidermodysplasia verruciformis. Thus, we propose to distinguish two other types of HPVs designated provisionally as HPV type 3 (HPV-3) and HPV type 4 (HPV-4), with J.D. and J.K. HPVs as prototypes, respectively. Malignant conversion of some epidermodysplasia verruciformis lesions is more frequently associated with HPV-4 than with HPV-3 infection.