A 71-year-old man underwent colonoscopy and multiple poly-pectomy. A few hours after the procedure he developed massive subcutaneous emphysema of the abdomen, chest, mediastinum, scrotum and both legs. Treatment was by conservative measures only. The emphysema gradually disappeared and he was discharged within a few days without sequelae. Subcutaneous emphysema is a rare complication of colonoscopy which has also been described after other endoscopic and radiological investigations of the gastrointestinal tract. It is due to a tiny laceration of the mucosal wall of the colon incurred during aggressive instrumentation, through which pass large quantities of air. The laceration is located underneath the peritoneal sac and the air flows into the retroperitoneum (closed or extraperitoneal perforation). The appearance of subcutaneous emphysema a few hours later, usually after leaving the hospital, is characteristic. In contrast to intraperitoneal perforation (open perforation), surgical intervention is not indicated and treatment is usually conservative. It includes complete cessation of oral alimentation, insertion of a nasogastric tube, IV drip, and correction of hydro-electrolytic or acid-base imbalances. The overall prognosis following such measures is excellent.