PURPOSE: The number of patients transported by the Helicopter Emergency Medical Service (HEMS) has increased recently. In our review of the Korean HEMS, there was no established helicopter utilization criteria or triage tool on the scene, so many patients with minor injuries were transported to tertiary care centers. The aim of this study is to evaluate the percentage of patients with minor injuries and to propose a more appropriate triage tool for predicting the need for transport to a tertiary care center. METHODS: The subjects of this study were 59 trauma patients transported to Asan Medical Center (AMC) from the scene by Seoul HEMS from January 2004 to December 2005. The Triage score (TS), Injury Severity Score (ISS), and modified Canadian Triage and Acuity Scale (mCTAS) were calculated as severity scales. Patients with minor injuries were defined as those with TS=9, ISS< or =15, and mCTAS> or =3. We evaluated the association of TS, ISS, and mCTAS with the appropriateness of transport. RESULTS: Many of the patients transported to tertiary medical centers were classified as having a minor injury: TS=9 group 35 cases (72.9%), ISS< or =15 group 30 cases (62.5%) and mCTAS> or =3 group 27 cases (56.2%). However, 56.2% (27/59) of the patients were appropriately transported according to need for admission or an operation. The more severely injured patients classified by TS, ISS, and mCTAS were more appropriately transported to a tertiary center (p<0.05). CONCLUSION: Many patients with minor injuries were transported to a tertiary center from the scene directly. The TS can be easily calculated by an emergency medical technician at the scene. Thus, we propose the TS as a useful triage tool for determining the necessity of transport to a tertiary center by helicopter.