Off-line prediction of the care to be provided to prehospital patients is inherently difficult. The Therapeutic Intervention Scoring System (TISS) score has proved useful for evaluating the degree of care provided to patients in intensive care settings, and may have prehospital application. We compared the Revised Trauma Score (RTS), Glasgow Coma Scale (GCS), and TISS scores in 575 prehospital patients transported from the scene of accident or illness by rotor-wing aircraft in an effort to uncover relationships between these parameters. Statistically significant Spearman rank order correlation coefficients were noted between RTS, GCS, and TISS in patients suffering from both traumatic and non-traumatic illness. The RTS and the GCS may be used as a guide to the degree of prehospital care that may be provided to victims of medical illness or trauma by helicopter emergency medical services (HEMS) systems.