Previous studies have found variable evidence suggestive of a role for human papillomavirus (HPV) in squamous cell carcinoma of the head and neck. In this study 49 cases of primary verrucous or squamous cell carcinoma from patients referred to a regional medical center were examined initially by Southern blot hybridization to detect HPV types 2, 6, 11, 13, 16, 18, and 32. Approximately 60% of carcinomas from certain head and neck sites, particularly the floor of the mouth, tongue, pharynx, piriform sinus, and larynx, were positive for episomal viral DNA of HPV-6, -11, -16, or -18. HPV DNA was found in some multiple tumors from separate sites of the same patient. Integration of viral DNA into the host cell chromosome was likely in a minority of the positive carcinomas, and no novel HPV DNA types were indicated by the hybridization analyses. Subsequently, DNA remaining from 30 of the carcinomas was examined by a more sensitive polymerase chain reaction amplification assay for DNA of HPV-6, -11, -16, and -18. Twenty-seven of the samples were positive for one or more HPV DNA types, with all positive carcinoma samples containing oncogenic HPV-16 or -18 DNAs. Almost all the patients examined were of the middle to older age group with a history of tobacco use. Although HPV infection of oral mucosa may be a frequent occurrence, a possible role for HPVs in the multifactorial etiology of head and neck carcinogenesis merits further epidemiologic investigation.