Over a 6-month period a prospective study was made of all patients undergoing operation for penetrating chest wounds. Three hundred and seventy patients with penetrating stab wounds of the chest presented to the Trauma Unit of the Groote Schuur Hospital (GSH) in this period, of whom 90% were managed non-operatively. A further nine patients with old infected haemothoraces were referred directly to the Cardiothoracic Unit from other centres. Of the 45 patients who required operation, 17 (38%) had suffered stab wounds of the heart. The condition of 22 patients (49%) deteriorated rapidly before operation, emphasizing the inherently unstable nature of such patients. The major indications for operation were cardiac tamponade (40%), continuing haemorrhage (24%), persistent air leak (12%) and retained infected haemothorax (24%). The major diagnostic criteria for tamponade were based on the central venous and arterial pressures, and their respective responses to resuscitative measures. Of the 45 patients who required operation, 5 (11%) underwent emergency room thoracotomy, 20 (44%) emergency operation within 90 min of admission and 6 (14%) operation for deteriorating condition after an initial period of observation; 3 (7%) underwent pleurectomy after 4 or 5 days for persistent air leak, and 11 (24%) required late thoracotomy for retained, infected haemothorax. There were three deaths, all in the emergency room thoracotomy group, giving an overall mortality of 7%. There were only two other major permanent complications (4%): one was severe neurological damage in a patient who had no discernible cardiac output on admission to the Trauma Unit, and the other was a myocardial infarction following a wound to a major coronary artery. Those patients (90%) treated non-operatively form part of a separate long-term study which will be reported at a later date.