Acute colonic obstruction is a medical emergency because of the potential for bowel ischemia, perforation, and sepsis with peritonitis if not rapidly and appropriately treated. There are numerous causes of acute colonic obstruction, which must be differentiated from colonic pseudo-obstruction, which also is considered a medical emergency. Management options include medical therapy, surgical therapy, endoscopic therapy, and interventional radiologic therapy. Self-expandable metal stents (SEMS) have gained acceptance for alleviating acute malignant colonic obstruction and in some situations for preoperative relief of acute benign colonic obstruction. This article reviews the approach to the patient who has acute colonic obstruction.