A variety of benign squamous epithelial lesions of the mucosa are associated with human papiUomaviruses (HPV). Recently virus-specific DNA was also detected in oral invasive carcinomas. In sections of 373 formalin-fixed and paraffin-embedded samples taken from benign and precancerous leukoplakias and squamous cell carcinomas, HPV DNA could be identified in 56 specimens by in situ hybridization technique. The biological significance of viruses of the HPV group in the carcinogenesis of oral epithelial lesions is still unknown.