The objective of this study was to determine the incidence and outcome of hepatitis C virus (HCV) infection after liver transplantation (OLT). Fifty-two transplanted patients were studied. Serum samples were examined for antibodies to HCV (anti-HCV) and HCV-RNA by PCR, before and after OLT. Patients were distributed into two groups: group 1 consisted of 24 patients (pretransplant anti-HCV positive) and group 2 consisted of 28 patients (pretransplant anti-HCV negative). One year after OLT, HCV-infected patients were evaluated by liver biopsy. HCV-RNA was detected in 28 of the 52 (53.9%) patients after OLT. Twenty-two patients in group 1 (96%) were reinfected. In group 2, acquired HCV infection was detected in six (21.4%) patients. At 6 and 12 months, one and five of six patients had seroconverted, respectively. Liver biopsy in 23 HCV-infected patients showed chronic hepatitis in 18 (78%) cases (2, chronic persistent hepatitis; 3, chronic lobular hepatitis and 13, chronic active hepatitis). Fourteen of the 23 (60.8%) patients were asymptomatic. Most symptomatic patients had chronic hepatitis with cholestasis. Overall, 18 of 20 cases of chronic hepatitis diagnosed in OLT recipients were HCV related. Mortality beyond 6 months after OLT was slightly higher in the HCV-infected group (P = 0.055). In conclusion, HCV reinfection is almost universal. Acquired HCV infection post-OLT is frequent. HCV-infected patients frequently develop chronic hepatitis. Most chronic hepatitis after transplantation are HCV related.