Detection of human papillomavirus-genomic DNA in oral epithelial dysplasias, oral smokeless tobacco-associated leukoplakias, and epithelial malignancies. Human papillomavirus (HPV) is an infectious agent that is increasingly associated with mucosal cancers, in particular cancer of the cervix. The present investigation was undertaken in an attempt to determine whether HPV could be easily detected in biopsies of oral tissues, specifically oral squamous cell carcinomas, oral epithelial dysplasias, smokeless tobacco keratoses, verrucous hyperplasia, and verrucous carcinoma. In situ DNA hybridization methods were used to isolate specific HPV genomes. Among 100 instances of benign leukoplakia, only 4% of non-tobacco-related and 10% of smokeless tobacco-related lesions harbored viral sequences. We were able to detect viral sequences in dysplastic lesions 3% of the time. Alternatively, 17% and 20% of the verrucous hyperplasias and verrucous carcinomas were positive for viral nucleic acids. Six percent of the squamous cell carcinomas harbored HPV. On the basis of these findings, it is concluded that HPV of known genotype can be identified in oral premalignant and malignant neoplasms. 