The ability to accurately triage trauma patients can be difficult in the prehospital environment. Prehospital trauma scoring systems have been developed with a goal of determining which patients should be transported immediately to a trauma center, thus benefiting from critical personnel and resource-intensive lifesaving interventions (LSIs). A resource-based endpoint, LSIs, therefore might be the optimal endpoint of prehospital triage scoring and could be used to determine where patients are transported. We hypothesized that simple physiologic data available immediately upon scene arrival would prove predictive of the need for a LSI. Trauma patients transported from the injury scene by helicopter were eligible for entry into the study. Prehospital physiologic data and interventions were timed and recorded by flight medical personnel, whereas hospital vital signs, injuries, and interventions were prospectively recorded from the inpatient records. The motor component of the Glasgow Coma Scale was used as an indicator of neurologic function. LSIs were procedures deemed lifesaving by a multidisciplinary panel of trauma experts. Physiologic data were collected from August 2001 to February 2002. Data were collected for 216 random patients transported by the Life Flight helicopter service. There were no differences between LSI and non-LSI patients in age, gender, or transport time, and 80 patients underwent 197 LSIs. The mean age was 33 +/- 17 years, 73% of patients were male, 90% suffered blunt injury, the injury severity score was 14 +/- 9, hypotension (systolic blood pressure of < 90 mm Hg) was present in 14% of cases, and the mortality rate was 6%. Penetrating injury and increasing injury severity score were associated with LSI. Univariate analysis of the physiologic data immediately available in the field revealed that SBP of < 90 mm Hg, motor score of < 6, delayed capillary refill, and increasing pulse were significantly associated with a LSI. However, multivariate analysis revealed that only SBP of < 90 mm Hg and motor score of < 6 were associated with a LSI. When both variables were abnormal, 95% of patients required a LSI; when both variables were normal, 21% of patients required a LSI. The presence of hypotension or decreased motor score was correlated with the need for LSIs. However, normotensive patients with normal motor scores still frequently required LSIs. Optimal discrimination of this group of patients will require new analytic approaches.