Galactose oxidase method was employed to detect the beta-D-Gal (1-->3) -D-Gal NAc residue of T-antigen present in the large intestinal mucus of 156 subjects. The positive rates of the test were 84.4%, 29.1%, and 7.2% in the mucus samples obtained from 32 patients with colorectal adenocarcinomas, 55 with polyps and 69 controls respectively. Chi-square test demonstrated that there were significant differences between the group of carcinoma and control (P < 0.001) as well as between also polyp and control (P < 0.01). The test had a high sensitivity (84.4%) and specificity (92.8%) in the diagnosis of colorectal cancer and may be used as a practical mass screening test for colorectal neoplasms.