32P-labelled DNA of HPV 16 which has been isolated and molecularly cloned from a cervical carcinoma (Dürst et al., 1983) was used to screen the cellular DNAs obtained from 20 different biopsies of Morbus Bowen or Bowenoid papulosis, respectively, by Southern blot analysis. Under conditions of differing stringency for the hybridization, HPV 16 DNA or related sequences were identified in 6 out of 10 cases of Morbus Bowen (4 out of 5 from a genital localization) and in 8 out of 10 biopsies from Bowenoid papulosis. One additional case of the latter disease contained DNA sequences of an HPV type not yet classified. There is evidence for the presence of another HPV DNA in two of the HPV-16-positive tumors. A large number of normal genital tissue samples were negative for HPV DNA.