A 56-year-old man was referred to our department in April, 2004. He had undergone colorectomy because of colon cancer at our hospital on August 16, 2002. Before colorectomy, liver metastic tumor was observed on abdominal ultrasonogram and computed tomogram. After surgical resection for primary colon cancer, 1500mg once weekly of 5-FU through reserver in common hepatic artery (CHA) was administered intraarterially from September 20, 2002. Serum transaminase levels were measured every month and remained within normal limits. Although serum transaminase levels remained normal during the follow-up period, liver dysfunction and ascites gradually developed. However, these rapidly abated after cessation of 5-FU treatment. The possibility of insidious liver injury, especially in cancer patients receiving long-term treatment, even if the patient has a normal serum transaminase level, should be considered when 5-FU is administered intraarterially or orally.