Background: Acute colonic pseudo-obstruction is often treated by colonoscopic decompression. Efficacy, safety, and outcome of endoscopic decompression was assessed. Methods: Colonoscopic decompressions from 1988 to 1994 were reviewed. Resolution without further endoscopic intervention was defined as clinical success. Results: Acute colonic pseudo-obstruction was diagnosed in 50 patients. Thirty-three cases followed surgery or trauma and 17 developed during severe medical illness. Orthopedic joint surgery was most common. Nineteen of 50 patients (38%) had severe underlying medical disease. Forty-one patients (82%) had one colonoscopic decompression with clinical success in 39 (95%). Nine patients (18%) required multiple (2 to 4) colonoscopic decompressions with clinical success in 5 (56%). A decompression tube positioned in the right colon (57%) and in the transverse colon (33%) had similar clinical success. In 8 procedures a decompression tube was not placed, with poor clinical success (25%). The overall clinical success of colonoscopic decompression was 88% (44 of 50). An endoscopic perforation occurred in 1 patient (2%). Overall hospital mortality was 30%. Conclusions: Colonoscopic decompression is effective and safe for acute colonic pseudo-obstruction that does not respond to conservative therapy. Most patients will respond to one colonoscopic decompression with decompression tube placement. Complete colonoscopy and cecal tube placement is unnecessary. (Gastrointest Endosc 1996;44:144-50.)