1. Nearly all recipients who are chronically infected with hepatitis C virus (HCV) at the time of liver transplantation will have HCV RNA detectable postoperatively. 2. HCV replication can begin as early as the first postoperative week. 3. HCV levels fall significantly during the anhepatic phase of liver transplantation and continue to fall during the first 12-24 hours posttransplantation. 4. Serum HCV RNA levels typically increase rapidly from the second week posttransplantation and peak by the fourth postoperative month. HCV RNA levels at one year posttransplantation are 10-20 fold greater than pretransplant levels. 5. Corticosteroid treatment for acute cellular rejection is associated with large increases in HCV RNA levels. 6. HCV RNA levels do not appear to vary with choice of calcineurin inhibitor. 7. Early HCV RNA levels are predictive of subsequent histological severity of recurrence. 8. A correlation between early levels of viremia and subsequent allograft injury suggests that initiation of antiviral therapy early in the posttransplant course might be desirable.