A patient undergoing emergency laparotomy for an acute abdomen developed fatal air embolism as a result of surgical manipulation of a cavitating metastatic lesion of the liver. The diagnosis was made at postmortem examination. This cause of air embolism has apparently not been reported before. The causes and management of air embolism are briefly reviewed. It is concluded that in exceptional circumstances when intubated patients are sent to a recovery area, the continuation of CO2 monitoring into the post-operative period should be considered.