Approximately half of the patients with type C hepatitis do not have a history of parenteral exposure. The route of nonparenteral infection remains unknown. To evaluate the possible role of body fluids, the existence of hepatitis C virus (HCV) RNA in saliva, urine, seminal fluid, and ascites was examined by "nested" polymerase chain reaction (PCR). Amplification of the HCV 5' noncoding sequences was carried out. The amplified product was confirmed by Southern blot hybridization and restriction endonuclease digestion. Among 34 patients with chronic liver disease who were positive for anti-HCV and serum HCV RNA, the prevalence of HCV RNA in body fluids was 100% (7/7) in ascites, 48% (15/31) in saliva, 24% (4/17) in seminal fluid, and 7% (2/29) in urine. The body fluids collected from 3 healthy subjects and 5 patients with chronic liver disease who were positive for anti-HCV but negative for serum HCV RNA were all negative for HCV RNA. Hence, the potential infectivity of body fluids in patients testing negative for serum HCV RNA can probably be discounted. Conversely, the presence of HCV RNA in saliva and seminal fluid of patients positive for serum HCV RNA suggests sexual and household contact as likely modes of nonparenteral transmission of type C hepatitis. Furthermore, the high prevalence of HCV RNA in ascites and saliva may have important implications in medical and dental practice.