To determine if out-of-hospital emergency medical services (EMS) time intervals are associated with unexpected survival and death in urban major trauma, a retrospective review was conducted of major trauma cases entered into an urban trauma system by an EMS system during a one-year period. Patients with unexpected death or unexpected survival were identified using TRISS methodology. The EMS response, on-scene time, transport time, and total EMS out-of-hospital time intervals were compared for the two groups using the unpaired t test (two-tailed analysis). Of 848 major trauma cases, there were 13 (1.5%) unexpected survivors and 20 (2.4%) unexpected deaths. Of those patients with complete EMS times, the mean out-of-hospital response time interval was significantly shorter for the unexpected survivors (3.5 +/- 1.2 minutes v 5.9 +/- 4.3 minutes; P = .04). The mean EMS on-scene time interval (7.8 +/- 4.1 minutes v 11.6 +/- 6.5 minutes; P = .06) and the mean transport time interval (9.5 +/- 4.4 minutes v 11.7 +/- 4.0 minutes; P = .17) also favored the unexpected survivor group. Overall, the total EMS time interval was significantly shorter for unexpected survivors (20.8 +/- 5.2 minutes v 29.3 +/- 12.4 minutes; P = .02). It was concluded that a short overall out-of-hospital time interval may positively affect patient survival in selected urban major trauma patients.