Post-orthotopic liver transplantation (OLT) recurrence of hepatitis C is virtually universal, but histological progression of disease is not. This study examines long-term clinical and liver histological features at and after OLT to elucidate factors predictive of hepatitis C recurrence and progression after OLT. A blinded retrospective review of clinical, serological, and histopathologic features of 65 patients who underwent OLT for hepatitis C and Non A Non B hepatitis was conducted. Histological findings of recurrent hepatitis C and progression (fibrosis, >or= grade 2 by last follow-up) were correlated with clinical parameters. Histological recurrence of hepatitis C was seen in 43 of 65 patients, with progression in 19 patients. Histological findings in the native liver and post-OLT biopsy specimen at the time of recurrence showed no correlation with hepatitis C recurrence and progression. Patients treated with azathioprine (AZA)-containing immunosuppressive regimens experienced less recurrence (6 of 17 v 37 of 48 patients; P < .005) and progression (1 of 17 v 18 of 48 patients; P = .014) than those without AZA as part of their immunosuppressive regimen. No difference was seen between patients treated with cyclosporine versus those administered FK506 (P > .05). Histological recurrence of hepatitis C after OLT is seen in 66% of patients with progressive disease and 29% of all patients. The grade of inflammation in the native liver at the time of OLT and time of recurrence is not predictive of progression. AZA-containing regimens reduce histological recurrence and progression of hepatitis C in post-OLT patients.