Approximately 67 different subtypes of HPVs have now been described. Regularly most of the cervical cancers are positive for HPV 16/18. Current research also indicates that HPVs may be involved in the development of benign tumours and also squamous cell cancers of head and neck. Studies establishing the presence of different HPV subtypes in oral cancers and precancers suggest the possibility of the virus as etiological factor in oral carcinogenesis too. In this study the prevalence of HPV 6/11, 16 and 18 infection and other exogenous risk factors like nicotine and alcohol in laryngeal cancers were studied. A total of 100 formalin-fixed and paraffin-embedded cancers, 41 glottic and 59 supraglottic, in patients aged 58 years, were detected by use of the E6 specific PCR for HPV DNA. Significantly more glottic cancers, 26 of 41 (63.4%), were positive for the investigated HPV's. HPV 16 was found in all positive cancers. This predominance of HPV 16 was also present in the supraglottic carcinomas, but only 10.2% (6 of 59) of the these groups were HPV positive. In both groups the patients with HPV 16 and/or 18 positive cancers, the exogenous risk factor was higher than with in HPV 16/18 negative tumours. Following infection, the virus either remains dormant or else undergoes active replication resulting in the synthesis of infectious virus. The integration of virus DNA into the host cell DNA may be the result of action of nicotine and/or alcohol. The integration event is the key of the carcinogenesis. The level of the risk factor in the patients with supraglottic tumours was significantly higher.(ABSTRACT TRUNCATED AT 250 WORDS)