Herical CT is superior to the conventional CT in the continuity of data in the axial direction. It can easily determine the cecum, terminal ileum and swollen appendix. In this series the usefulness of Herical CT was studied in subjects who had or were suspected of acute appendicitis and whose preoperative definite diagnoses appeared difficult to be made. Subjects were 16 patients who were seen at the hospital because of a right lower abdominal pain and were suspected of acute appendicitis on palpation. The appendix was determined as a structure projecting from the cecum and ending blindly on Herical CT. No contrast medium was used. As a result, swollen appendix was able to be observed in nine out of 16 cases and three cases were indicated to have coprolith or intraperitoneal abscess, all of which were diagnosed as appendicitis. The remaining four cases had no meaningful findings in the imaging which were ruled out from appendicitis cases. In a comparison with laparotomy findings and clinical courses, the correct diagnosing rate of this imaging was 100%. Herical CT can offer clear images compared with those of the conventional CT; dramatically increases determinating rate of the appendix because of its superiority in the continuity in the axial direction; and greatly contributes to decide operative indication and to confirm the location of the appendix during surgrey.