Recurrence of hepatitis C virus (HCV) after liver transplantation is common and is associated with high blood levels of HCV RNA. Higher blood levels of HCV may promote body fluid expression of the virus. We tested 152 body fluid specimens from 33 patients with chronic hepatitis C, 21 of whom had undergone prior liver transplantation. All patients had hepatitis C viremia, as determined by a reverse-transcription polymerase chain reaction (PCR) to the 5' noncoding region. The virus was quantitated in serum by the branched chain DNA assay (bDNA). Body fluids (33 sputum, 33 saliva, 33 urine, 32 tear, 9 vaginal, and 12 semen samples) were analyzed using PCR for HCV RNA. Serum HCV RNA by bDNA in the posttransplantation group was 255 +/- 229 x 10(5) compared with 50 +/- 56 x 10(5) eq/mL in the patients who did not undergo transplantation (P = .01). All urine, tear, and semen specimens were negative for HCV RNA. Five of 21 (24%) posttransplantation patients had detectable HCV RNA using PCR in oral secretions compared with 0 of 12 patients who did not undergo transplantation (not statistically significant). However, 5 of 11 patients with serum HCV RNA by bDNA results greater than 150 x 10(5) eq/mL had positive RNA in oral secretions compared to 0 of 22 patients with bDNA less than 150 x 10(5) eq/mL (P = .01). Posttransplantation patients were more likely to have bDNA levels exceeding 150 x 10(5) eq/mL (11 of 21 v 1 of 12, P = .03). Patients within the first year of transplantation were particularly prone to viral RNA levels exceeding 150 x 10(5) eq/mL (8 of 9 v 3 of 12, P = .01). We conclude that HCV RNA can occasionally be detected using PCR in oral secretions after liver transplantation. This is more likely during the first year posttransplantation when blood levels of HCV RNA often exceed 150 x 10(5) eq/mL by the branched chain DNA assay. Whether or not these observations represent an increased risk of transmission of infection during the early posttransplantation period is not certain.