The "ACC/AHA Guideline Update for the management of patients with unstable angina and Non-ST-segment elevation myocardial infarction", which was published in 2002, emphasizes the continuous risk stratification of patients with unstable angina and non-ST-elevation myocardial infarction (NSTEMI), during the course of its diagnosis and management. The main purpose of the risk stratification in patients with acute coronary syndrome is to identify high risk patients, and give them optimal treatment, in an optimal environment, and to prevent inappropriate, or excessive, treatment for patients with a low risk of an adverse outcome. For patients with an intermediate risk at the initial evaluation, further risk stratification, with noninvasive diagnostic tests, is recommended, which may provide a guide for the next treatment plan. For the initial risk stratification of patients with suspected acute coronary syndrome; the clinical history, a physical examination, a 12-lead electrocardiography and cardiac specific biomarkers, are critically important. Cardiac specific troponins, T and I, are especially useful for the diagnosis of acute coronary syndrome, and they may also provide important information for the risk stratification. There are two main strategies for the management of acute coronary syndrome; the early invasive and the early conservative, strategies. There are many reports suggesting the positive effect of the early invasive strategy, compared with the early conservative strategy, on the prognosis of high risk patients. Low molecular weight heparin and GP-IIb/IIIa receptor blockers have been reported to provide a positive effect on the prognosis when used in high risk patients. Therefore, the risk stratification is important during the diagnostic procedure, and may provide an important guide in the management of patients with acute coronary syndrome.