Acuminate condylomas from the penis (n = 17) and anus (six cases), three anal/penile giant condylomas, anal Bowen's disease (four cases), and intraanal squamous cell carcinomas with associated condylomatous changes (10 cases) including two verrucous carcinoma were studied for human papillomavirus (HPV) infections with nick translated, biotinylated cDNA probes for HPV 6, 11, 16 and 18. In addition, six cases of flat white penile lesions designated as lichen sclerosus et atrophicus were examined. Reannealed complementary DNA strands were detected in situ with either immunoenzyme or immunogold protocols. The in situ hybridizations resulted in 1/6 positive penile lichenoid lesions, 12/17 positive penile acuminate condylomas, 6/6 positive anal acuminate condylomas (including two condylomas with cellular atypias), 2/3 positive giant condylomas, 1/4 positive anal bowenoid lesions, and 4/10 positive keratinized squamous cell carcinomas, two of them being verrucous carcinomas. All penile/anal condylomas and two giant condylomas harboured HPV 6 and/or 11 DNA. The five positive carcinomas (carcinoma in situ/invasive cancer) contained HPV 6 and/or 11 in two cases (including the verrucous carcinomas), and HPV 16 and/or 18 in three cases (one carcinoma in situ, two invasive carcinomas). Recurrent malignancies were seen in one case to harbour the same HPV type as the primary lesions (HPV 16). In one particular patient, a double infection with HPV 16 and HPV 18 was demonstrated in distantly located malignant tumours. Our study confirms the restrictions and the value of non-isotopic hybridization methods applied to archival tissues, and extends the knowledge on the presence and distribution of HPV infections at anogenital sites.