Volvulus of a megacolon probably occurs more frequently than is generally appreciated. Weeks (1) reported an example and reviewed some 63 cases which he gathered from the literature. Half of these patients had previously experienced attacks of obstipation, abdominal pain, and distention. It is not unreasonable to assume that volvulus, either partial or complete, occurs not infrequently in patients with megacolon and can be reduced before strangulation or necrosis ensues. Report of a case of megacolon complicated by volvulus in the sigmoid region and reduced during barium enema examination follows: Case Report A. M., a white male aged 39, entered Mount Sinai Hospital on Jan. 12, 1944, complaining of abdominal cramps which had been increasing in severity for two weeks prior to entrance. The patient stated that he was “normally constipated,” but that constipation had been more troublesome in the past two months. Only mucus and very little fecal matter, the latter in the form of small hard nodules, were passed at intervals of several days. No blood was observed in the stool, but tenesmus was present. The abdomen had become increasingly distended during the last few months. The appetite was fairly good but the patient complained of some nausea several days before entering the hospital. The family history was essentially negative. The patient was well developed and well nourished, and subacutely ill. The temperature was 98° F., pulse 104, respirations 20, blood pressure 124/76. Examination of the head, neck, and chest was essentially negative. The abdomen was moderately distended and tympanitic throughout. No masses were palpable and no definite abdominal tenderness was present. The bowel sounds were diminished in intensity but slightly increased in number. The clinical impression was “acute mechanical obstruction of the distal colon, cause undetermined but carcinoma to be excluded.” Blood determinations on admission to the hospital showed 14.5 gm. of hemoglobin and a white cell count of 7,850, the differential count being normal. Urinalysis was essentially negative; only a few leukocytes were demonstrated per high power field. The blood Kline test was negative. Roentgen examination of the abdomen in the recumbent and upright positions on the day of admission to the hospital showed great distention of the large intestine apparently down to about the level of the distal descending or sigmoid colon. The right half of the colon contained a considerable amount of fecal material. Marked dilatation and elongation of the overlapping distended loops of large bowel were observed (Fig. 1). A few loops of small intestine were seen to contain small quantities of gas, irregularly distributed. In the upper abdomen a few fluid levels were demonstrated, but there was no evidence of free gas in the peritoneal cavity.