A quality assurance audit of all interhospital patient transports from 17 June 1985 through 31 December 1989 by Connecticut's critical care helicopter system was performed to determine the number of medically appropriate and justified flights. There were 1,839 transports reviewed using nationally established criteria. Flights not fulfilling any of these criteria (n = 401) were reviewed in detail by a panel consisting of medical and nursing representatives. During this case by case review, additional acceptable criteria for transport were developed. The audit determined that 1,792 (97%) of interhospital transfers were justified for helicopter emergency medical transport. The use of these national criteria along with the proposed additional criteria is recommended to health care personnel in the decision to transport a patient to a tertiary care hospital by air. In addition, these criteria should be prospectively utilized by aeromedical flight programs for quality assurance review of appropriateness of helicopter interhospital requests.