Background and Objectives: In early phase of acute chest pain, diagnosis of acute myocardial infarction (AMI) is often difficult in emergency department (ED) due to non-diagnostic ECG and cardiac markers. Fatty acid binding protein (FABP) has recently been shown to be an earlier diagnostic marker for AMI than CK-MB and troponin. The aim of this study was to evaluate the diagnostic value of rapid semiquatitative FABP assay in patients with suspected AMI and normal troponin/CK-MB. Subjects and Method: We enrolled consecutive 83 patients presenting to the ED due to suspected AMI with normal troponin-I and CK-MB within 5 hours after the onset of chest pain. The diagnosis of AMI was based on clinical findings, results of serial ECG and troponin. Rapid FABP test measured by CardioDetect quant (Rennesens GmbH, Germany). The ideal cutoff value of FABP for AMI was calculated by receiver operator characteristic (ROC) curve analysis. Results: The AMI was diagnosed in 36/83(43.4%). Baseline demographic characteristics were similar between AMI and non-AMI group. Symptom to ER arrival time was 186.6짹121.4 minutes in AMI group. Mean values of FABP was higher in AMI. (48.16 짹 35.05 vs. 12.70 짹 6.22 ng/dl, p<0.001). The ROC curve area for the rapid FABP test was 0.88 (CI; 0.807-0.957, p<0.001). At a cutoff value of 14.5 ng/mL, the sensitivity, specificity, positive and negative predictive value for AMI were 83.3 %, 78.7 %, 75% and 86.1%, respectively. Conclusions: Rapid FABP assay might be a useful diagnostic test for AMI in patients with normal cardiac markers presenting within 5 hours after the onset of chest pain.