BACKGROUND: Prediction of mortality in trauma patients is an important part of trauma care. Trauma scoring systems are the current methods used for prediction of mortality. We aimed to evaluate and compare the performances of Injury Severity Score (ISS) and New Injury Severity Score (NISS) in firearm injuries. METHODS: Records of 135 firearm-injured patients who applied to Uludag University Emergency Department between January 2001 and December 2005 were analyzed retrospectively. All patients' data, including age, gender, cause of injury, initial vital signs, injury region, Glasgow Coma Scale (GCS), Revised Trauma Score (RTS), mortality, operation data, and final diagnosis, were collected, and ISS, NISS and Trauma and Injury Severity Score (TRISS) were calculated. RESULTS: Mortality rate was 12.6%. The patients' mean GCS, RTS, ISS, NISS, and TRISS scores were 13.41 +/- 0.31, 10.65 +/- 0.26, 17.04 +/-1.20, 21.94 +/- 1.45, and 9.52 +/- 2.37, respectively. The patients were divided into two groups as ISS = NISS (53.3%) and ISS < NISS (46.7%). CONCLUSION: ISS and NISS both performed well in mortality prediction of firearm injuries. NISS demonstrated no superiority to ISS for prediction of mortality in these patients.