ObjectiveTo evaluate the use of daily Acute Physiology and Chronic Health Evaluation (APACHE) II scoring in the prediction of individual mortality rates for intensive care unit (ICU) patients.DesignA prospective study of consecutive patients admitted to four university-affiliated ICUs.SettingMedical-surgical ICUs of four tertiary care academic hospitals.PatientsDaily data from 3,350 consecutive ICU admissions, excluding postoperative cardiac patients, were collected from January to December 1991.Measurements and Main ResultsDaily APACHE II scores were calculated for all patients and correlated with both ICU and hospital mortality. The ability of an absolute level or a predetermined algorithm, based on these scores, to predict mortality was examined. Day 1 APACHE II scores ranged from 0 to 55 (mean 18). We were unable to replicate the suggestion by Chang et al. that 100% hospital mortality was predicted by the following APACHE II scores: a) >35 at admission; b) 30 to 35 at admission, with a decrease of ≤3 from day 1 to day 2; or c) >27 on any day, with an increase of >2 from the previous day. We were unable to adjust these criteria to avoid a false prediction of death with any remaining useful sensitivity. Mortality rates of 158 (69%) deaths per 229 patients, 68 (62%) deaths per 110 patients, and 110 (48%) deaths per 230 patients were obtained, respectively, for these criteria.ConclusionsAdmission or daily APACHE II scores do not predict individual patient mortality. The adjustments needed in the algorithm that was used to avoid a false prediction of death render sensitivity so low that it would be impractical to limit therapy on this basis alone. (Crit Care Med 1994; 22:1402–1405)