The Abdominal Trauma Index (ATI) was devised to quantify the risk of complications following abdominal trauma. With scores greater than 25, the risk of postoperative complications became exponential. The purpose of the present study was to determine if: 1) the organ risk factors previously assigned were more statistically valid; and 2) the addition of physiologic variables would enhance the prediction of postinjury intra-abdominal sepsis. Fifteen abdominal organ systems and 17 physiologic variables in 300 consecutive patients were analyzed to determine ability to predict intraabdominal sepsis. There were no significant differences in predictive ability between the old and new organ risk factors. The addition of physiologic factors did not enhance the prediction of intra-abdominal sepsis. This clinical study demonstrates that: 1) the risk of intra-abdominal sepsis increases with increasing ATI score; 2) the previous (1979-initial) organ risk grading concept is statistically valid; 3) six of the 15 organ systems warrant a change in their relative rank order (1989-revision); 4) the addition of demographic, physiologic, and immunologic variables did not significantly improve the prediction of intra-abdominal sepsis.