Prospective identification of patients who will not survive has been proposed as a means of limiting utilization of medical resources including critical care. This study prospectively compared prediction of outcome for surgical ICU patients by clinical assessment and the APACHE II score. Five hundred seventy-eight patients were assessed within 24 hours of admission by the ICU attending physician and predicted to live or die. An APACHE II score was calculated in that same time period. All data were stored in a data base and compared with actual SICU outcome. There were 40 deaths in 578 patients (6.9%). The clinical assessment had an overall accuracy of 95.2% vs. 90.9% for APACHE II. The Pearson correlation coefficients for the two methods of prediction were 0.59 for clinical assessment and 0.44 for APACHE II. Predictive power was not greatly improved by combining both prediction methods. Over 40% of patients predicted to die by both methods actually survived. This study demonstrates that clinical assessment is superior to APACHE II in predicting outcome in this group of surgical patients, although the difference is small. In addition, this study suggests that neither clinical assessment nor the APACHE II score, when obtained within 24 hours of admission, is very reliable at predicting which surgical ICU patients will die.