Background 64 multi-detector computed tomography(MDCT) is a recently introduced as a diagnostic tool for chest pain with high accuracy. However, guidelines for the clinical application of MDCT are limited especially comparing with conventional diagnostic strategy.We present the interim findings of ongoing prospectively randomized trial 'Usefulness of MDCT as a first diagnostic approach in acute chest pain patients���. Methods We prospectively enrolled the patients with acute chest pain who visit ER from April 2006. Exclusion criteria was ST elevation myocardial infarction(MI), unstable vital sign, uncontrolled arrhythmia, renal failure, hypersensitivity to contrast dye and clinically no possibility of angina. Patients were divided into 3 clinical categories based on history, physical exam, and electrocardiogram: 1)definite angina with uncertainty of regarding MI(group1), 2)probable angina(group2), 3)probable not angina(group3). After categorized, patients were randomized to either conventional evaluation and treatments(control group) or immediate 64-MDCT and CT-guided treatments(MDCT group). We evaluate the length of stay, admission rate, accuracy of diagnosis, and major adverse cardiac event(MACE) and clinical diagnosis in 1 month after discharge from ER. Results Ninety-two patients were included(47 in MDCT, 45 in control). Control and MDCT group had similar baseline characteristics. In high risk group(group1), no benefit was found between groups. However, in intermediate and low risk group(group2 and 3), there was a trend of decreased unnecessary admission(p=0.056) in MDCT group. MDCT group with low risk(group3) had a shorter length of stay compared with control group, although it did not reach the statistical significance(13.6 vs. 7.1 hour). In the subgroup analysis, positive predictability of coronary artery disease(CAD) by MDCT was 85% and by conventional work-up 74%(p=0.43). There was no difference in MACE between groups at 1 month���s follow-up with a very low rate. Conclusions MDCT as a first diagnostic approach to acute chest pain can reduce the unnecessary admission and possibly reduces the length of hospital stay in patients with clinically low and intermediate risk of CAD.