CT pictures from 59 lesions of advanced colon cancer including rectal cancer were reviewed to evaluate a role of CT in preoperative staging diagnosis. CT findings were recorded following general rules for clinical and pathological studies on cancer of colon, rectum and anus, proposed by Japanese Society for Cancer of Colon and Rectum. 1) Tumors were detected in 90% of advanced colon cancers. 2) Sensitivity in local extension (S factor) was 58.0%. 3) Sensitivity in lymph node involvement (N factor) was 50.0%. 4) Sensitivity in final staging diagnosis, dividing colon cancer into two groups below st II and above st III, was 63.3%. 5) Further study should be necessitated to provide useful information for preoperative staging diagnosis of colon cancer.