The authors reviewed the records of 569 patients transported by an emergency helicopter service to evaluate its impact on the outcome of patients with multisystemic injuries. A Total Trauma Score for each patient was computed. A number of other factors were also considered, including the nature of the injury, number of systems injured, origin and duration of flight, resuscitative maneuvers, number of blood transfusions given and the timing of operations required to treat the injury. The service was then rated utilizing strict specific guidelines as either essential, helpful or not a factor, in the preservation of life and/or limb in each case. A fourth group was comprised of patients who expired as a result of their injuries. The air transport service was essential to 16.5% and helpful to 10.9% of patients. In spite of rapid evaluation and maximal intervention, 102 (17.9%) of the patients died. The group for which air transport was judged "not a factor" (54.7%) consisted of patients whose injuries would not have proven fatal had their transportation to the tertiary care center been delayed. Retrospective analysis of the data available to the tertiary care center at the time of the decision to transfer the patients by air revealed that it was not possible to differentiate those patients who did not benefit from the service from those for whom the service was judged essential or helpful. Even though 17.9% of the helicopter transported patients died at some time during their period of hospitalization, they did receive the benefit of prompt sophisticated evaluation and management of their injuries.(ABSTRACT TRUNCATED AT 250 WORDS)