This study examined the initial haemodynamic and oxygen transport patterns in 24 patients with severe blunt thoracic trauma in whom immediate monitoring with femoral and pulmonary artery catheters was required after admission to the intensive care unit. All patients required mechanical ventilation and were studied before receiving inhalational anaesthesia and within 12 h of injury. Two groups of patients were identified; nine patients (group 1) had an impaired left ventricular stroke work index (LVSWI) and 15 patients had a normal LVSWI (group 2). There were no significant differences in the abbreviated injury scale score for the chest, the total injury severity score, or the mean ages of the two groups. There were significant differences in stroke volume index, 32 versus 56 ml m-2 (P less than 0.001), and cardiac index, 3.2 versus 5.3 l min-1 m-2 (P less than 0.001), and therefore in oxygen delivery, 469 versus 852 ml min-1 m-2 (P less than 0.001), despite apparently adequate volume expansion using the same protocol and clinical criteria in both groups. Oxygen consumption was not significantly different in the two groups, 135 versus 157 ml min-1 m-2, because of a higher oxygen extraction ratio in group 1, 29 versus 19 per cent (P less than 0.001), and hence lower mixed venous oxygen saturation, 73 versus 82 per cent (P less than 0.02). Seven patients in group 1 died (78 per cent) compared with two in group 2 (13 per cent). Early depression of cardiac function is associated with poor outcome in patients with thoracic trauma, and measurements of oxygen transport variables may influence resuscitation and the timing of surgical procedures.