Epidemiologic and biomolecular evidence suggests that human papillomavirus (HPV) infection may be associated with the development of head and neck cancers. To clarify the role of HPV in larynx carcinoma, 25 patients were studied for the presence of viral DNA, possible virus integration into the cellular genome, and viral expression both in neoplastic tissues and in neighbouring normal mucosa. Twelve of 25 patients with neoplasia (48%) showed negative results for HPV sequences, and 13 (52%) showed positive results. Among the latter group of patients, seven were HPV-16 positive, five were HPV-6, and one was HPV-45. No multiple infections were detected. The physical status of the HPV genome was analysed by three methods: polymerase chain reaction (PCR), bidimensional agarose gel electrophoresis, and in situ hybridisation. Viral integration into the host genome occurred in 43% of cases of HPV-16 and in 20% of cases of HPV-6. Viral RNA expression was detected by reverse transcription-PCR only in HPV-16-positive tumours. The pattern of expression was consistent with an active role of HPV in cellular transformation. In conclusion, the present work suggests that HPV infection may be involved in some cases of laryngeal carcinoma. However, the transformation mechanisms might be different from those currently accepted for anogenital cancers.