Forty-eight cases of Ogilvie's syndrome, colonic pseudo-obstruction, presenting between 1983 and 1989 were retrospectively reviewed to assess the results of colonoscopic decompression and to identify potential etiologic factors. Three patients had spontaneous resolution with medical treatment. Forty-five patients required 60 colonoscopic decompressions: 38 (84 percent) were successfully treated using colonoscopy; five (11 percent) required an operation; and two died within 48 hours of colonoscopy from medical causes. No complications or deaths were the result of colonoscopy. Twenty-nine patients (64 percent) were successfully treated with a single colonoscopy. One-third of patients required serial decompressions. Average cecal diameter in patients with successful colonoscopic decompression was 12.4 cm but was larger for patients requiring more than one colonoscopy (13.3 cm) and for those who failed colonoscopic therapy (13.4 cm). The spine or retroperitoneum had been traumatized or manipulated in 52 percent of patients. Patients with Ogilvie's syndrome were being treated with narcotics (56 percent), H-2 blockers (52 percent), phenothiazines (42 percent), calcium-channel blockers (27 percent), steroids (23 percent), tricyclic antidepressants (15 percent), and epidural analgesics (6 percent) at diagnosis. Electrolyte abnormalities included hypocalcemia (63 percent), hyponatremia (38 percent), hypokalemia (29 percent), hypomagnesemia (21 percent), and hypophosphatemia (19 percent). Colonoscopic decompression in Ogilvie's syndrome is safe and effective management. Multiple pharmacologic and metabolic factors, as well as spinal and retroperitoneal trauma, appear to alter autonomic regulation of colonic function, resulting in colonic pseudo-obstruction.