Backgrounds: The Thrombolysis in Myocardial Infarction (TIMI) risk score (TRS) has proven value in predicting prognosis in unstable angina/non ST-elevation myocardial infarction (NSTEMI) as well as in ST-elevation myocardial infarction. But TRS system has little implication as to the extent of myocardial damage in high-risk patients with NSTEMI. Thus we sought to evaluate validity of TRS system in NSTEMI and to propose an alternative risk stratification model. Methods: A total of 1,621 patients (63.6짹12.2 years of age; 1,043 males) with NSTEMI were enrolled in the Korea Acute Myocardial Infarction Registry (KAMIR). The baseline clinical characteristics and TRS were recorded including biomarkers such as Tn-I, NT-proBNP, and hs-CRP. We analyzed the risk for major adverse cardiac events (MACE) during a period of 6-month follow-up. Results: TRS system had good correlation with MACE for patients in the low and intermediate group. MACE rate was 3.8% for TRS 1, 9.4% for TRS 2, 10.7% for TRS 3, and 12.3% for TRS 4 (HR=1.29, p=0.026) but had poor correlation when the high-risk group was included (p=0.128). Among the biomarkers, elevated NT-proBNP levels above 75 percentile had the best predictive value for MACE (HR=2.61, p=0.001) independently of other risk factors. Among the clinical risk factors, Killip class above III showed good correlation with MACE (HR=0.302, p<0.001). So we devised an alternative clinical scoring system by including these two variables reflecting left ventricular dysfunction: age > 65 years old, history of ischemic heart disease, Killip class above III and elevated pro-BNP levels above 75 percentile. This modified scoring system, when tested for validity, showed a good predictive value for MACE (HR=1.64, p<0.001). Conclusions: Compared with the traditional TRS, the novel alternative scoring system based on age, history of ischemic heart disease, Killip class, and NT-proBNP showed a better predictive value for 6-month MACE in high-risk patients with NSTEMI.