pneumothorax is a possible dangerous situation which may arise suddenly during anaesthesia. The diagnosis is one of exclusion, as initial changes in vital signs (cardiorespiratory decompensation and difficulty with ventilation) are non-specific, and other causes of such changes are more common, whereas local signs may be difficult to obtain, especially without full access to the chest. Diagnosis of pneumothorax during general anaesthesia is difficult, especially as this problem is uncommon. Although there are a number of well recognized high risk conditions, pneumothorax may occur all of a sudden in a patient with no known risk factors. A small, undiagnosed, asymptomatic pneumothorax may become a tension pneumothorax on doing positive pressure ventilation of the lungs after induction of or during anaesthesia. As the systemic signs of pneumothorax are non-specific and the local signs difficult to elicit if access to the chest is restricted, a high level of suspicion and a systematic approach is required for the rapid detection of this potentially hazardous problem1. Pneumothorax is an uncommon problem, especially during general anaesthesia, when the patient cannot complain of respiratory difficulty or pain, and with positive pressure ventilation, which increases the risk of a tension pneumothora