We have investigated the incidence of oral precancerous lesions among the inhabitants in a hepatitis C virus (HCV) hyperendemic area. Two oral surgeons examined the oral lesions of 685 (295 men, 390 women; mean age of 56.1 years) adult inhabitants, hyperendemic area of HCV infection. All sera were examined for antibodies to HCV (anti-HCV) and serum HCV RNA. Anti-HCV or HCV RNA were detected in sera from 84 (12.3%) or 61 (8.9%) of all. Oral lichen planus (OLP), leukoedema, or leukoplakia were observed in 10 (1.5%), 82 (12%), or 47 (6.9%) subjects, respectively. The incidences of OLP, leukoedema, and leukoplakia in the subjects with HCV infection were significantly higher than those without HCV. These results indicated that HCV may play an important role in oral cancer and related precancerous lesions. Moreover, our study also emphasized the need for periodic examination of the oral cavity in patients with HCV.