A closed-book, multiple-choice examination following this article tests your under standing of the following objectives:1. Compare and contrast 5 scoring systems and their ability to predict morbidity and mortality in the cardiac patient population. 2. Identify preoperative, intraoperative, and postoperative variables when using a prospective study. 3. Describe the performance of each scoring system. Methods Consecutive patients admitted to a cardiac surgical intensive care unit (CSICU) were prospectively studied. Data on the preoperative condition, intraoperative parameters, and postoperative course were collected. EuroSCORE II, CASUS, and scores from 3 general severityscoring systems (APACHE II, SAPS II, and SOFA) were calculated on the first postoperative day. Clinical outcome was defined as 30-day mortality and in-hospital morbidity. Results A total of 150 patients were included. Thirty-day mortality was 6%. CASUS was superior in outcome prediction, both in relation to discrimination (area under curve, 0.89) and calibration (Brier score = 0.043, c 2 = 2.2, P = .89), followed by EuroSCORE II for 30-day mortality (area under curve, 0.87) and SOFA for morbidity (Spearman ρ = 0.37 and 0.35 for the CSICU length of stay and duration of mechanical ventilation, respectively; Wilcoxon W = 367.5, P = .03 for probability of readmission to CSICU). Conclusions CASUS can be recommended as the most reliable and beneficial option for benchmarking and risk stratification in cardiac surgery patients.