Objective: To determine if all increase in the third-ICU-day acute physiology score (APS) of the APACHE (acute physiology and chronic health evaluation) III prognostic system call identify potentially ineffective care. Design: Retrospective cohort study. Setting: Academic medical center. Patients: Adult patients with first-ICU-day predicted mortality rate greater than or equal to 80%. Measurements: Demographics, ICU admission source. admission type, ICU admission diagnosis. first- and third-ICU-day, APSs, APACHE III score, APACHE III-predicted hospital mortality. hospital discharge status, 100-day survival, and ICU and hospital length of stay. Results: A total of 302 patients (age [mean +/- SD], 64.7 +/- 15.8 years. 54.3% male gender) were included in the study. Respiratory failure was the most common reason for ICU admission. Nonoperative admissions accounted for 94.7%. The first- and tlrird-ICU-day APSs were 106.8 +/- 19.S and 70.5 +/- 29.9, respectively. The first- and third-ICU-day predicted hospital mortality rates were 87.8 +/- 5.3% and 86.5 +/- 14.8%. respectively. The hospital mortality rate was 61.3%, and the 100-day survival rate 28.5%. The third-ICU-day APS was higher than the first-ICU-day APS in 34 patients (11.3%). Only 2 of these 34 patients (6%) survived to hospital discharge, compared to 115 of 268 patients (43%) without ail increase in A-PS (p < 0.0001). Of the two hospital survivors with increased APS, only one patient survived 100 days after hospital discharge. In predicting 100-day mortality the sensitivity of all increase in the third-ICU-day APS was 15.3% (95% confidence interval, 11.1 to 20.7%), specificity was 98.8%, (95%, confidence interval, 93.7 to 99.8%), positive predictive value was 97.1%, (95%, confidence interval, 85.1 to 99.5%), and negative predictive value was 31.7% (95%, confidence interval. 26.4 to 37.5%). Conclusions: A higher APS on the third ICU day. compared to the first ICU day, identifies potentially ineffective care in patients with the first-day predicted hospital mortality rate greater than or equal to 80%.