Carcinoembryonic antigen (CEA) is frequently used in the diagnosis of the colorectal carcinoma. CA242 is a novel unique tumor-associated antigen characterized by higher tumor specificity and sensitivity for colorectal cancer, as compared with other mucin antigens. In this study, preoperative levels of serum CEA and CA242 were measured in 63 cases of colorectal carcinoma. It was disclosed that the positive rate of CA242 was higher than that of CEA, particularly in patients with colon cancer. The combined determination of CEA and CA242 significantly increased the sensitivity and accuracy in the detection of colorcctal cancer as compared with the use of CEA alone (P<0.01). In patients with advanced disease the positive rate was markedly elevated, especially in patients with liver metastasis. The results indicate that the combined use of CEA and CA242 assays is an useful adjunct diagnostic measure for colorectal carcinoma, and is helpful in the assessment of the stage of the disease as well as in making treatment plan.