Recurrent hepatitis C infection is an important cause of progressive fibrosis, cirrhosis, and graft loss following orthotopic liver transplantation. Treatment for posttransplant recurrence of hepatitis C with interferon-based therapy is difficult but results in loss of detectable virus in up to 30% of patients. However, the durability of viral clearance and the associated histologic response in this setting is unknown. The aim of this study was to determine whether viral loss in response to antiviral therapy is durable and associated with improvement in liver histology. All liver transplant recipients who received interferonbased treatment for recurrent hepatitis C virus (HCV) at the University of Florida from 1991 to 2002 were included in this study. Patients who lost detectable HCV after treatment with interferon alone or in combination with ribavirin were followed to assess the durability of viral response and its impact on liver histology. One hundred nineteen transplant recipients were treated with interferon or combination therapy. Twenty-nine (20 men, 9 women; mean age, 54 yrs [range, 42-74 yrs]) lost detectable HCV RNA and remained virus negative for at least 6 months after discontinuing therapy (sustained viral response[SVR]). The mean follow-up after discontinuing therapy was 24.7 months (range, 6 -70 mos). Our study cohort included one patient with SVR following interferon monotherapy and 28 patients with SVR following combination therapy with interferon plus ribavirin. All patients remained HCV RNA negative (assessed by polymerase chain reaction or branched-DNA assay) during follow-up of up to 5 years. Liver histology assessed 2 years after treatment showed less inflammation compared with before treatment in 50% and showed no change in 38%. By 3 to 5 years post-treatment (n β«Ψβ¬ 15 recipients), inflammation was reduced in 60% and remained unchanged in 33%. Fibrosis stage at 2 years improved by > 1 stage in 27 %, remained unchanged in 38 %, and worsened in 35% despite viral clearance. At 3 to 5 years, the fibrosis stage had improved in 67%, remained unchanged in 13%, and worsened in 20%. Both grade of inflammation and fibrosis stage improved by 3 to 5 years posttreatment compared with baseline histology (p < 0.05). In conclusion, loss of HCV after treatment of recurrent chronic hepatitis C with interferon and ribavirin is durable, and the durability of the SVR is associated with improvement in hepatic inflammation and regression of fibrosis. (Liver