The Advanced Trauma Life Support (ATLS) course sponsored by the American College of Surgeons Committee On Trauma (ACSCOT) presents a standardized method of initial trauma care. This study attempted to measure any changes in morbidity and mortality in trauma patients after the introduction of ATLS training. Over a 3-year period (May 1996 to September 1997-pre-ATLS period; December 1997 to April 1999-post-ATLS period), 63 trauma patients with an Injury Severity Scale (ISS) > or =16 (n = 31, pre-ATLS and n = 32, post-ATLS) were prospectively studied in two community teaching hospitals. There was no significant difference in mortality rate between groups (48% [15 of 31] pre-ATLS vs. 30% [10 of 32] post-ATLS; P = .203, Fisher exact test). Mortality rates within the ISS range of 16 to 25 were 64% (nine of 14 pre-ATLS) versus 29% (five of 17 post-ATLS), and for the ISS 26 to 35 subgroup, 40% (four of 10 pre-ATLS) versus 25% (two of eight post-ATLS), and within the ISS 36 to 75 subgroup, 29% (two of seven pre-ATLS) versus 43% (three of seven post-ATLS). There was a significant difference in mortality during the first 60 minutes after admission: 0.0% post-ATLS versus 24.2% pre-ATLS (P = .002, Fisher exact test (95% confidence interval ranged from 12-45% in the pre-ATLS group and 0-11% in the post-ATLS group). According to the TRISS methodology (a worldwide-accepted mathematical method to calculate chances of survival through logistical regression),ATLS improved outcome from sub-"Major Trauma Outcome Study" (MTOS) standard results (z = -2.9 to a MTOS standard result z = -0.49). Our data demonstrate that introduction of the ATLS program significantly improved trauma patient outcome in the first hour after admission, as well as improvement from sub-MTOS standard to MTOS standard levels.