The positive rates for NCC-ST-439 in cases where other tumor markers were negative were 16.8% for CA19-9-negative cancer cases and 23.5% for CEA-negative cancer cases. The positive rates obtained using a combination of these three markers were 86% for pancreatic and cholangiocarcinomas, and at least 65% for hepatocellular, rectal and colonic and mammary carcinomas. The following combinations of tumor markers were the best from the standpoint of diagnostic efficiency: NCC-ST-439 + CA19-9 for pancreatic carcinoma, NCC-ST-439 + AFP for hepatocellular carcinoma, and NCC-ST-439 + CEA for rectal and colonic carcinoma. In cases which were positive preoperatively, 83.3% became negative after curative surgery, which reflected the clinical course very well. These results indicate that NCC-ST-439 improves the diagnostic rate in combination with other tumor markers because of its high specificity, and it was evaluated as useful for the monitoring of therapeutic effects.