Electrocautery is widely used for dissection of tissues and cauterization of blood vessels. A visible plume of smoke is produced, which has an unpleasant odour and can induce acute and chronic inflammatory changes in the respiratory tract'. Airborne particles arc not effectively filtered or evacuated by operating room scavenging systems and facial masks only offer protection from large particles. Little is known about the chemical composition of this smoke and the health risks to the operating room staff have not been identified. The aim of this study was to determine the chemical composition of electrocautery smoke produced in the course of standard colorectal surgery.