Pseudoobstruction of the large bowel occurs as acute distention of the colon, usually in a high risk and seriously ill patient without any mechanical obstruction. Massive distention of the colon results in perforation of the cecum and fecal peritonitis and is associated with a very high mortality rate. Laparotomy with cecostomy is the recommended surgical therapy for this problem which carries a mortality rate of over 20 percent. We have used the colonoscope to decompress the distended colon, and especially the cecum, in 10 patients with Ogilvie's syndrome, with a 90 percent success rate and no deaths or complications. The surgeon should follow the several technical guidelines mentioned herein for successful and safe performance of the procedure. These guidelines include a tap water enema of about 1,000 ml before the procedure, avoidance of the liberal use of air insufflation during the procedure, and blind insertion of the colonoscope. This procedure is not indicated in any patient with signs of peritonitis and perforation.