To deterrnine the applicability of the Acute Physiology and Chronic Health Evaluation (APACHE II) scoring system in ICU, 552 ICU patients who had been admitted from March 1, 1992 to February 28, 1993 were analysed. The mean APACHE II score of nonsurvivors was significantly higher than that of survivors (p<0.01) and there was significant relationship between mortality rate and APACHE II score [Mortality rate(%) =2.994XAPACHE II score-14.987 (r=0.97, p<0.001)). However, the majority of postoperative patients had scores less than 20 points and the postoperative patients were more unevenly distributed. These results suggest that the APACHE II score may be useful for analyses of ICU patients but its application in postoperative patients must take into consideration the patient's clinical condition.