The APACHE II scoring system has been promulgated as a useful tool in the assessment of the severity of injury and prognosis for acutely ill patients. The physiologic basis for stratification is weighted toward older patients with chronic medical conditions. Recently, the APACHE II system has been proposed as a method for determining diagnosis related group (DRG) reimbursement for individual trauma patients. The present study applied the APACHE II scoring system to 280 patients with blunt or penetrating trauma who had documented systolic blood pressure < 90 mm Hg. Fifty-seven (20%) died of their injuries within the first 24 hours. APACHE II scores were recorded both in the emergency room (ED) and at 24 hours following admission. Injury Severity Scores (ISS), Revised Trauma Scores (RTS), and TRISSCAN were calculated. The APACHE II (n = 223) recorded at 24 hours (2.5 +/- 0.2) was significantly less than that recorded in the ED (6.6 +/- 0.3, p < 0.05, Mann-Whitney analysis). Using regression analysis, there was no correlation between APACHE II and ISS if recorded in the ED (r2 = 0.06) or 24 hours following admission (r2 = 0.08). APACHE II also demonstrated a poor correlation with the length of hospital stay (r2 = 0.03 [ED], = 0.19 [24 hours]). Whereas APACHE II may be helpful in defining severity of disease among patients with acute-on-chronic medical conditions, the classification lacks an anatomic component, which is essential to assess the magnitude of acute injury in patients who are typically otherwise healthy.