We report a case of multicentric hepatocellular carcinoma that developed in a 74-year-old man 3 and 6 years after interferon (IFN) treatment for chronic hepatitis C, despite sustained virologic, biochemical, and histological improvement. Initially, serum hepatitis C virus RNA was positive and the patients' serum level of alanine aminotransferase (ALT; 82 IU/ml) was abnormal. Hepatitis B virus (HBV) in the serum was negative for surface antigen, surface antibody, core antibody, and DNA. The patient was started on 10 x 10(6) international units (IU) of IFNalpha, 3 days a week for a total of 24 weeks. After the IFN therapy, the patient demonstrated a normal serum ALT level, and was continuously negative for HCV-RNA, and histology improved from chronic active hepatitis to chronic persistent hepatitis. Follow-up studies with ultrasonography (US) every 3 months and computed tomography (CT) every 6 months revealed no space-occupying lesion (SOL) for 3 years after IFN treatment.US-guided biopsies of two 15-mm hypoechoic SOLs in segments eight (S8) and seven (S7) 34 and 74 months, respectively, after IFN treatment showed well-differentiated hepatocellular carcinoma (HCC). Clinical data, imaging studies, and histologic examinations showed that both tumors were multicentric HCC. Further studies may provide insights into the possible role of HCV in hepatocarcinogenesis in patients demonstrating HCV eradication by IFN treatment.