Objective: To determine the efficacy of prehospital use of military anti-shock trousers (MAST) on the mortality of trauma patients. Data Sources: MEDLINE was used to search the literature related to the above topic from 1966 key words. Japana Centra Revuo Medicina (Japanese Collection of medical articles) CD was also used to search Selection: Non-randomized controlled trials (non-RCTs), randomized controlled trials (RCTs), and case reports on the effect of MAST on mortality in adult trauma patients were included. The studies were further subgrouped according to methodologic quality (case reports, non-RCT, and RCT). Meta-analysis was performed on 2 RCTs reported. Main Results: More than 20 case reports suggested improvement in survival as a rusult of using MAST in trauma patients. Four non-RCTs that evaluated 1,570 patients and 2 RCTs that evaluated 1,032 patients met the respective inclusion criteria. Among the non-RCT studies, MAST reduced mortality in one study and increased it in another study, but it did not change it in the other of 2 studies. MAST was not associated with any significant changes in mortality in either RCT. Meta-analysis of the 2 RCTs showed that MAST did not reduce mortality in the overall or subgroup analysis based on injury sites, blunt or stab wounds, or transport time. It revealed no significant difference in length of ICU or hospital stay between the treated and controll groups. Conclusion Prehospital use of MAST in trauma patients was not demonstrated to be effective in reducing mortality or length of ICU or hospital stay.