Biopsies of 13 penile cancers (PC), from patients living in regions of Uganda with a high incidence of genital cancers, were studied for the presence, molecular characteristics and physical state of DNA related to that of human papillomavirus (HPV) types 6, 11, 16, 18, 31 and 33. HPV DNA sequences were detected in all PC specimens by dot/Southern blot analyses and by gene amplification of DNA sequences highly conserved among several HPVs. HPV 16 DNA sequences were found in one PC; DNA sequences with low homology to HPV16 or HPV18 were present in all other samples. Viral DNA is primarily integrated in the cellular DNA. To isolate and characterize a possible highly oncogenic HPV, a genomic library of the DNA extracted from the PC-8 biopsy has been constructed in the EcoRI arms of the EMBL4 phage. A single phage containing 8.30-kb HPV16-related sequences has been identified and the 3 segments of 0.45, 0.65 and 7.2 kb, released by EcoRI digestion, have been independently subcloned in pUC18 for further analysis.