To evaluate the relationship between APACHE III score and mortality in critically ill adult ICU patient, we studied the 548 patients who were admitted to the ICU from June 1, 1994 to January 31, 1995. We did not include patients with burn injuries, patients aged less than 15 years, or chest pain patients, in order to rule out myocardial infarction and unsatisfactory data files. There were 120 multiple trauma patients, 68 sepsis patients, 62 hemorrhagic shock patients, 20 multiple organ failure patients, and 120 patients with, among other conditions, drug intoxication, diabetic ketoacidosis, renal failure, hepatic encephalopathy, and cerebral hemorrhage or infarction. The APACHE III scores of survivors and non-survivors were analyzed with Chi-square test and compared. The number of nonsurvivors was 168 patients, and the overall mortality rate was 30.7%. there was a positive correlation between a high APACHE III score and mortality ; all patients with more than 90 points expired. The average points of the survivors was 34.52 土 15.48 and of nonsurvivors was 77.74 土 31.37. The difference between each group is significant statistically. The average APACHE III points was 47.8. The APACHE III score is a good prognostic tool to predict the mortality rate in ICU adult patients, and can be used for selection of patients and for ICU admission/discharge. It can also be used to compare the efficacy of intensive care in different hospitals.