In terms of colorectal carcinoma, the fecal occult blood test is widely used for mass survey, but has many complicated problems to be overcome. Telomerase activity has been reported in a wide range of malignancies. We have examined telomerase activity of intestinal lavage solution collected from 16 colorectal carcinoma patients and from 10 volunteers (control) by the method of telomeric repeat amplification protocol (TRAP) assay. Patients drunk polyethylene glycol-electrolyte lavage solution (PEG-ELS) before examination. Sample solutions were collected by colonoscope at the beginning of colonoscopy. The telomerase activity from colorectal carcinoma patients were positive 9/16 (56.3%) including 2 cases of early stage. In volunteers, were positive 1/10 (10.0%). This method has, therefore, possibility for a new useful method of diagnosis for colorectal carcinoma.