Background Several prognostic risk scores have been developed for patients with coronary artery disease, but their comparative use in patients with non–ST-segment elevation acute coronary syndromes (NSTEACS) undergoing percutaneous coronary intervention (PCI) has not been examined. We therefore investigated the accuracy of the Synergy Between PCI With Taxus and Cardiac Surgery (SYNTAX) score, Clinical Synergy Between PCI With Taxus and Cardiac Surgery score (CSS), New Risk Stratification (NERS) score (NERS), Age, Creatinine, Ejection Fraction (ACEF) score, Global Registry for Acute Coronary Events (GRACE) score, and Thrombolysis in Myocardial Infarction (TIMI) score for risk assessment of 1-year mortality, cardiac mortality, myocardial infarction, target vessel revascularization, and stent thrombosis in patients with NSTEACS undergoing PCI. Methods The 6 scores were determined in 2,094 patients with NSTEACS treated with PCI enrolled in the angiographic substudy of the ACUITY trial. The prognostic accuracy of the 6 scores was assessed using the c statistic for discrimination and the Hosmer-Lemeshow test for calibration. The index of separation and net reclassification improvement (NRI) were also determined. Results Scores incorporating clinical and angiographic variables (CSS and NERS) showed the best tradeoff between discrimination and calibration for most end points, with the best discrimination for all end points and good calibration for most of them. The CSS had the best index of separation for most ischemic endpoints and displayed an NRI for cardiac death and myocardial infarction (MI) compared to the other scores, whereas NERS displayed an NRI for all-cause death and target vessel revascularization. The 3 scores—CSS, NERS, and SYNTAX—were the only scores to have both good discrimination and calibration for cardiac mortality. Conclusions In patients with NSTEACS undergoing PCI, risk scores incorporating clinical and angiographic variables had the highest predictive accuracy for a broad spectrum of ischemic end points.