Decompensated liver disease associated with chronic hepatitis C virus (HCV) infection is the most common indication for liver transplantation. It was shown previously that greater pretransplantation HCV titers are associated with relatively poor patient and graft survival. The tolerability and efficacy of antiviral therapy in patients with decompensated liver disease are not known. We conducted a pilot study to determine the likely tolerability and efficacy of pretransplantation antiviral therapy with interferon alfa-2b, with or without ribavirin. HCV RNA-positive patients at or near the top of their respective waiting lists were randomly assigned to one of three treatment regimens until the time of liver transplantation: (1) group A, interferon alfa-2b, 1 × 106 U/d; (2) group B, interferon alfa-2b, 3 × 106 U three times weekly; or (3) group C, interferon alfa-2b, 1 × 106 U/d, plus ribavirin, 400 mg twice daily. Less than half the patients screened met entry criteria, with thrombocytopenia and leukopenia the most common reasons for exclusion. Fifteen patients were administered antiviral therapy; three patients in group A and six patients each in groups B and C. Loss of detectable HCV RNA was seen in 33% of patients, whereas 55% had a decrease in viral titers on therapy. Twenty-three adverse events occurred, including 20 serious adverse events. Thrombocytopenia was the most common adverse event. Two infectious complications occurred; one of these had a fatal outcome. We conclude that although pretransplantation antiviral therapy may reduce HCV titers in a minority of patients who meet treatment initiation criteria, adverse events associated with therapy are frequent and often severe in patients with Child's class B and C cirrhosis.