AbstractWe prospectively studied the normal vermiform appendix in 100 patients undergoing computed tomography (CT) of the abdomen and pelvis in order to assess its rate of visualization, isolate factors affecting its successful identification, and determine its most frequent position. Our standard CT protocols were followed, as dictated by the patient's clinical circumstances; this usually meant employing a 10 mm slice‐thickness at 15 or 20 mm intervals. The appendix was confidently identified in 27 of the 79 patients who had not undergone previous appendectomy. It was most commonly seen in a retroileal position. It had a mean maximum outer diameter of 5.7 mm (range 3–10 mm) and was most often seen as a thin‐walled, air‐filled tube. Its visualization was unaffected by the position of the cecal pole in a cranio‐caudal direction, the amount of intraabdominal fat, the type of radiographic contrast media administered, or the patient's sex. Computed tomography thus appears to be a useful, if limited, radiological method of examining the normal appendix. Our study suggests that, in vivo, the uninflamed appendix may not be most commonly situated in a retrocecal position, as reported in surgical and postmortem studies. © 1993 Wiley