BACKGROUND: The acute physiology and chronic health evaluation (APACHE) II score is considered to be a precise predictor of mortality and a useful basic research tool. A lower APACHE II score means a better prognosis of patients, which means that these relatively low risk patients are more likely to benefit from the improved patient management than the higher predicted mortality admissions. Therefore, these patients are obvious targets for intensive care and for decreasing the level of intensive care unit (ICU) mortality. METHODS: This study reviewed the medical records of 729 patients, whose APACHE II scores on the ICU admission day were 10 or less, from June 1, 2001 to May 31, 2002 in University Hospital. The data of the patient's age, gender, disease category, first admission or readmission, APACHE II score, length of stay at the ICU and the hospital were reviewed. RESULTS: The average mortality rate of the patients who had an APACHE II score of 10 or less was 4.1%. The mortality of the cancer patients (8%) was significantly higher than the other disease groups. The mortality of the readmitted patients was significantly higher than the mortality of the patients who were admitted to the ICU for the first time. CONCLUSIONS: Among the patients in the ICU with a low APACHE II score, the mortality of cancer patients was high. The mortality of the readmitted patients was significantly higher than in those on the first admission.