Opinions differ as to the best method of preparing the abdomen for radiographic examination, but there is at least one point upon which there is little disagreement, i.e., the most important prerequisite for a refined diagnosis is that the intestines be as clean as possible. As has been recently stressed (1), it is essential that the cecum as well as the sigmoid be well prepared for large bowel examination and that the intestinal mucosa throughout permits the adhesion of an even coating of barium to the intestinal wall. Any preparation should be essentially nontraumatic to the patient, inexpensive in terms of materials, time, and personnel, and should achieve consistently reliable results. Our experience is with a group of outpatients who come from a radius of up to three hundred miles to receive one or multiple examinations and then return home. We prefer a routine that offers minimal inconvenience to the patient before or after his visit to the department, but we must depend upon a system that will yield consistent accuracy in the diagnostic examination. Basic routine which we have found satisfactory is as follows: Bowel Preparation Details: 1. Two oz. of castor oil the previous evening (4:00–8:00 p.m.) 2. Nothing by mouth after a light evening meal on the night before the examination (mild dehydration emphasized) 3. Dihydroxyphenylisatin enema (utilizing 10 mg in tap water) on arrival in the department. 4. Delay of less than an hour before the study. It has been our experience that the well known irritant, castor oil, in the amount of two ounces the previous afternoon or evening gives us best preliminary results. We have attempted multiple other substitutes but the results were not as satisfactory and often the side-effects were as frequent as with castor oil. We prefer a low-fat diet and mild dehydration the night before the examination. Personnel within the x-ray department have the responsibility of carefully administering a final washout enema after the patient arrives in the department. The patient is instructed to lie on the right side, then prone, and again on the right side, but no significant other delay in evacuation is requested. Opinions vary widely regarding the use of additives to a final washout enema, as well as an additive to the barium suspension itself. Indeed, one recent opinion is the decision made by the Federal Drug Administration regarding the use of tannic acid. Since 1956 it has been our routine to use dihydroxyphenylisatin in tap water for the preparation enema and prior to oral cholecystography, excretory urography, the barium enema examination, the double air-contrast enema, as well as endoscopy.