The ability of the Pediatric Trauma Score (P.T.S.) to predict injury severity and mortality was evaluated by analysis of its relationship with the Injury Severity Score (I.S.S.) of 615 children entered into the National Pediatric Trauma Registry (N.P.T.R.). Mean age was 8.2 years and mortality was 3.5%. Mean I.S.S. of survivors was 8.1 in comparison to 59.7 for nonsurvivors. Linear regression coefficient determined from analysis of these variables produced a slope of -3.7 with a statistically significant correlation of P.T.S. to I.S.S. (p less than 0.001; r2 = 0.89). Analysis of the mortality for each cohort of patients with the same P.T.S. identified three categories of mortality potential. Children whose P.T.S. was greater than 8 had a 0% mortality. Children whose P.T.S. was between 0 and 8 had an increasing mortality related to their decreasing P.T.S. (r2 = 0.86), and children whose P.T.S. was below 0 had 100% mortality. This study documents the direct linear relationship between P.T.S. and injury severity, and confirms the P.T.S. as an effective predictor of both severity of injury and potential for mortality.