Mortality predictions calculated using scoring scales are often not accurate in populations other than those in which the scales were developed because of differences in case-mix. Scoring systems should be validated to be used in a different population. Probabilities of ICU death for critically ill trauma patients were calculated using the scores ISS, NISS, RTS, APACHE II, ASCOT, TRISS, TRNISS. The scores were assessed for discrimination using receiver operator characteristics area under the curve ROC AUC and for goodness-of-fit using Hosmer-Lemeshow test. Both TRISS and ASCOT performed better than the anatomic and physiologic scores as regard calibration and discrimination. The replacement of ISS with NISS in TRISS (TRNISS) resulted in better discrimination but poor calibration. We recommend the combination of APS and NISS to be applied on a larger scale and validated.