The patient, a 61-year-old man, had sustained injuries in a traffic accident at the age of 26, for which he received a blood transfusion. Since 1988 (age, 49 years), abnormal hepatic function had been detected, and, because of the presence of hepatitis C virus antibodies, he was diagnosed as having type C chronic hepatitis. Based on a liver biopsy that was conducted in July 1992 (age, 53), a histological diagnosis of chronic active hepatitis (F(1)/A(2)) was made. Over a period of 6 months, starting in 1992, the patient was treated with interferon (IFNalpha-2a; total dosage, 720 MU). At the end of this regimen, the alanine aminotransferase level was normalized and serum hepatitis C virus-ribonucleic acid was negative. This condition was maintained until August 1996 (age, 57), after which the patient stopped reporting to our hospital. In June 2000 (age, 61) when he was hospitalized for an adhesive ileus, a small hepatocellular carcinoma (a solitary lesion measuring 18 mm in diameter) at S(8) was found, and it was extirpated by a segmental excision in July. The case is introduced to call attention to the need for longterm follow-up observation, even after effective IFN therapy.