Hospital competition for air ambulance business has resulted in implementation of a helicopter service before the medical staff can prepare for the increased patient load. We reviewed the effect of an air ambulance on an already established trauma center (TC) by analyzing the impact of the helicopter trauma patient load during the initial year of operation. The helicopter carried a three-member flight crew consisting of a pilot, paramedic, and critical care nurse. Admission data of all flights from February 1982 through February 1983 were reviewed. Of the 325 air missions launched, 192 (59%) were for the transport of trauma victims. One hundred forty (73.6%) patients were transported from local hospitals, the remaining 52 (26.4%) from the accident scene. Ninety per cent of the injuries were due to motor vehicle accidents. Forty-nine per cent of the flights occurred on weekends and 68.8% were launched between 7:00 P.M. and 3:00 A.M. The average flight times from hospital and accident scenes were 37 min 30 sec and 13 min 30 sec, respectively. Of all trauma missions flown, 126 (65.8%) were considered new or 'captured' by the air ambulance system and brought to the TC. Thirty-seven (19.3%) patients died in flight, were DOA, or died within 1 hour of TC arrival. Eighty per cent of the deaths were from massive head injuries. The average injury severity score was 35.58 (all patients), 32.9 (survivors), and 45.80 (deaths).(ABSTRACT TRUNCATED AT 250 WORDS)