Serum TPA and CEA level were measured in patients with gastric or colon cancer during the course of surgical treatment, and those clinical utility was evaluated. Both markers level were shown to be highest in colon cancer, followed by gastric cancer, benign diseases, and healthy subjects. Late stage patients, especially inoperable patients or patients in recurrence showed significantly high TPA and CEA level compared to early stage patients. Both markers were considered to be useful not only postoperative following up for recurrence but also preoperative evaluation for resectability and prognosis and postoperative evaluation for the treatment itself.