Purpose: Injury severity score (ISS), a widely used scoring system, is used to define the severity of trauma in multiple-trauma patients. Nevertheless, ISS cut-off value for predicting the outcome of multiple-trauma patients has not been confirmed. Thus, this study was performed to determine the more useful method for predicting the outcome for multiple-trauma patients: the ISS or the number of anatomical Abbreviated injury scale (AIS) injury regions. Methods: for 195 consecutive patients who a regional emergency medical center, we analyzed the ISS and the number of anatomical AIS injury region. The patients were divided into four groups based on the ISS and the number of anatomical AIS regions. We compared intensive-care-unit (ICU) admission days and hospitalization days and ICU stay ratio (ICU admission days/hospitalization days) between the four groups. Results: In the groups with an ISS more than 17, the results were not significantly different statistically the group with 2 anatomical AIS injury regions and more than 3 anatomical AIS injury regions. Also, in the group with an ISS of 17 or less, the results were the same as those for patients with an ISS more than 17 (p>0.05). Among the patients with 2 anatomical AIS injury regions, patients with an ISS more than 17 patients had more ICU admission days and a higher ICU stay ratio than patients with an ISS 17 or less. Also, Among the patients with 3 anatomical AIS injury regions, the results were the same as those for patients with 2 anatomical AIS injury regions. Conclusion: Patients with high ISS, regardless of the number of anatomical AIS injury regions had significantly longer ICU stays and higher ICU admission ratio. Thus, the ISS may be a better method than the number of anatomical AIS injury regions for predicting the outcomes for multiple-trauma patients.