A case of massive subcutaneous emphysema following colonoscopic polypectomy is reported. The incidence of colonic perforation following colonoscopy is 0.1% and may be intraperitoneal or retroperitoneal. Intraperitoneal perforation is usually immediately apparent and likely to require urgent surgical exploration. The development of subcutaneous emphysema or a pneumoscrotum suggests a retroperitoneal perforation and in the majority of cases management is conservative. Contrast studies are often unhelpful but plain x-rays may help to distinguish between intraperitoneal and retroperitoneal perforations.