Management of massive exsanguinating hemorrhage is a major challenge in acute trauma care. The value of military antishock trousers (MAST) in this setting is controversial. In selected instances, thoracotomy with aortic cross-clamping may be effective and often is used as the "gold standard" to which new experimental therapy is compared. Previous animal research with an occluding aortic balloon catheter (Percluder) has shown this technique to be physiologically similar to aortic cross clamping. The Percluder was more effective than the MAST plus volume replacement in controlling hemorrhage and prolonging four-hour survival from blunt splenic trauma in an animal model. We have used the Percluder in 23 patients with life-threatening hemorrhage. There were 15 trauma cases, five cases of ruptured abdominal aortic aneurysm, and three others. Only nine of 23 patients (39%) had vital signs when the balloon was inserted; all showed an increase in arterial blood pressure of about 50% to 100% (P less than .0001). Two of 15 trauma victims (13%) and four aneurysm patients in whom the balloon was used were long-term survivors. One trauma victim lived for two weeks before dying of ischemic complications after 90 minutes of balloon aortic occlusion. Overall survival rate was 26%. This study was uncontrolled and occlusion therapy was not randomized. Eleven of 12 attempts to place the catheter by femoral cutdown were successful. Seven of 12 attempts (58%) to place the catheter percutaneously were successful. The six insertion failures were due to an inadequately small introducer, inability to identify arterial pulses in moribund patients, or difficulty in cannulating the femoral artery because of proximal occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)