In 117 patients with colorectal cancer, the serum levels of CEA, TPA, CA 19-9, IAP, and, AFP have been compared with the clinical findings. The combined assay of 5 tumor markers were found to be useful for the screening of colorectal cancer. Excluding the AFP, positive rate of the markers for colorectal cancer was higher than that for breast cancer (p less than 0.01) and similar to that for gastric cancer. The serum levels of TPA, CEA and CA 19-9 correlated with the histological progression. Thus, they may be an indicator of the degree of lymph node metastasis, liver metastasis, the histological depth, and also may be useful in evaluating the prognosis of patients with colorectal cancer.