CT is an accurate and noninvasive method for determining the extent of disease in the pelvic neoplasms including the assessment of anorectal tumor. Accurate staging is faced an ability to discriminate normal structure from abnormal one and to identify all sites of tumor. Author performed air insufflation of the rectum to increase the contrast of the rectal lumen relative to its wall and tumor mass in 30 cases of anorectal carcinoma. Preoperative CT staging was compared wtih postoperative pathological staging in order to determine the accuracy and significance of air insufflation method. The results were as follows; 1. The CT scan using air insulfflation detected all of 30 anorectal carcinoma(sensitivity=100%), and had an overall accuracy of 80%. 2. The detection inperirectal invasion had 88% sensitivity, 86.7% accuracy and the detection of lymphnode metastasis had 53% accuracy. 3. This technique was expected as a method for detection of early rectal carcinoma.