We prospectively enrolled the patients with acute chest pain who visited ED. Exclusion criteria were myocardial infarction (MI) with ST elevation, unstable vital sign, uncontrolled arrhythmia, renal dysfunction, hypersensitivity to contrast media and pregnancy. Patients were allocated into 3 categories based on history, physical exam, and electrocardiogram: 1) definite angina with uncertainty of regarding MI (high risk), 2) probable angina (intermediate risk), 3) low likelihood of angina (low risk), and then randomized to either receive MDCT immediately (MDCT group), or not (control). We compared diagnostic accuracy, length of stay in ER, admission rate, and major adverse cardiac events (MACE) and clinical diagnosis in 1 month after discharge from ED.