We investigated whether carcinoembryonic antigen (CEA) could be used to predict the response and survival of patients treated with 5-FU. Between 1984 and 1994, 58 patients with unresectable hepatic metastases from colorectal carcinoma were enrolled in this study. Forty-three patients underwent resection of the primary colorectal malignancy, and a catheter was inserted into the hepatic artery during the operation (HAI group). Fifteen patients received no adjuvant therapy (non-HAI group). Patients with CEA values reduced by greater than or equal to 30% at 2 months after the start of 5-FU infusion had a significantly longer survival period than patients with a decrease of <30%. Terminal cases in CEA reduced by greater than or equal to 30% group revealed that CEA re-elevation was observed at 7 months, and the patients died 8 months later at 15 months. Our findings suggest that serum CEA monitoring is useful for predicting the survival time following 5-FU hepatic arterial infusion.