Antiviral therapy after liver transplantation (LT) using interferon (IFN) and ribavirin (RBV) can achieve a sustained virological response (SVR) rate ranging from 20% to 45%. The aims of our study were to assess efficacy and tolerability of therapy, effect on fibrosis progression and the importance of the initial fibrosis stage to outcome. A total of 113 hepatitis C virus (HCV)-infected LT patients received 133 courses of IFN (standard, n = 29, pegylated IFN [pegIFN], n = 104) and RBV (75% genotype 1). Early virological response (EVR), end-of-treatment (EOT), and SVR were obtained in 74%, 55%, and 38%, respectively. EVR, completion of treatment, viral load before therapy, genotype non-1, and use of pegIFN were predictive of SVR, but only EVR remained in the multivariate analysis. SVR was obtained in 45% patients who received a second course of therapy. Paired biopsies at baseline, at EOT and at long-term were available in 42 patients. The mean fibrosis stage remained stable in patients with SVR and increased in patients without response. Rejection episodes were observed in 6% of patients. Tolerability of therapy decrease in patients with fibrosis stage ≥3 on baseline liver biopsy. A total of 20% of them died or were retransplanted due to liver failure as opposed to 1% of patients who had fibrosis stage <3. In conclusion, IFN and RBV achieved SVR in 38% of patients. EVR is independently associated with SVR. Fibrosis stage remained stable in patients with SVR and increased in nonresponders. Fibrosis stage ≥3 was associated with a high rate of liver failure, arguing for an early introduction of antiviral therapy. Liver Transpl 14:1766–1777, 2008. © 2008 AASLD.