Twelve patients who had sustained trauma presented at the emergency department with either asystole or profound hypotension. All underwent thoracotomy and temporary cross clamping of the descending thoracic aorta as part of the resuscitative measures; all received massive amounts of fluids and cold blood and underwent prompt surgical intervention. In none of these patients was there evidence of myocardial, peripheral nerve, neurologic or renal damage. One patient had residual cortical blindness. Measures were taken to preserve renal function before, during and after aortic cross clamping. These included the avoidance of nephrotoxic antibiotics, limit of clamping time to the minimum effective period, intermittent release of the aortic clamp, and intraoperative administration of osmotic diuretics or furosemide, or both. Other factors which may have contributed to these results were the youth of these patients, the absence of cardiac, renal or metabolic diseases and the hypothermia resulting from the administration of large amounts of cold blood. We concluded that temporary cross clamping of the descending thoracic aorta should be performed only for patients with massive exsanguine trauma who have cardiac arrest or who do not respond to other intensive resuscitative measures.