Background and Objectives : The aim of this study was to find out suitable models for evaluation and management of patients suspected of having acute coronary syndrome (ACS). Methods : 460 patients (mean age 63.2짹 11.7, 67.2% males) were evaluated in a nationwide prospective Korea Acute Myocardial Infarction Registry (KAMIR) study between November 2005 and August 2007. Thrombolysis In Myocardial Infarction risk score (TIMI RS), Global Registry of Acute Coronary Events (GRACE) and TIMI risk index were all calculated at each patients. Risk scores were divided into 3 risk groups as followed: GRACE RS (1-108, 109-140, 141-372), TIMI risk index (<30, 30-60, >60), and TIMI RS (0-2, 3-4, 5-7). Results : Coronary intervention was performed in 70.4% (n=324) of patients, success rate of intervention was 84.2%. Angiographic findings were divided to normal or non-significant (n=75, 18.8%), significant 1-vessel (n=138, 34.6%), 2-vessel (n=95, 23.8%), 3-vessel (n=86, 21.6%) and left main coronary artery disease (n=5, 1.3%). 194 patients were admitted coronary care unit (CCU), in-hospital mortality rates was 1.7%. Mortality or myocardial infarction (MI) in a year was 3.0%. The best prediction tool was GRACE RS (AUC) for in-hospital death or myocardial infarction (area under the curve: 0.88, confidential interval: 0.80-0.96] and in a year (AUC 0.79, CI=0.72-0.87). According to GRACE RS, significant differences existed in the presence of significant coronary lesion (p=0.002), successful intervention (p=0.0001), extent of coronary artery (p=0.004), more 3-vessel or left main lesion (p=0.002), more CCU admission (p=0.002). However, other risk models such as TIMI risk index and TIMI risk score did not show significant differences in these parameters, except for successful intervention with TIMI risk index. Conclusion: GRACE RS is suitable for predicting mortality in a patient with a low to intermediate likelihood ACS. It was correlated with the presence, extent of coronary artery disease, and with the clinical and angiographic severity.