This study was designed to determine the effect of military antishock trousers (MAST) use on the presenting emergency center trauma score (TS) in an urban prehospital setting. Sixty-eight patients were assigned randomly to study and control groups in a prospective investigation of the use of MAST on injured patients with hypotension. Thirty-two control patients, whose mean initial systolic BP was 59 +/- 32 mm Hg, and 36 MAST-treated patients, whose mean initial BP was 55 +/- 31 mm Hg, were found to be well matched for age; sex; type and location of injuries; initial field TS; response, field management, and transport times; and the total amount of intravenous crystalloid infused. Our results demonstrated no significant difference between the control and MAST-treated groups in the presenting emergency department TS (9.8 +/- 6.6 vs 10.6 +/- 5.9). These data conflict with the widely accepted belief that MAST will always enhance conventional support for improving the prehospital condition of injured patients with significant hypotension.