Background: Acute myocardial infarction (AMI) in patients (pts) with normal or insignificant coronary artery has been recognized. We hypothesized that the coronary spasm with or without myocardial bridge (MB) may play an important role in the pathogenesis of AMI. We investigated the incidence and clinical characteristics of spasm documented in a series of Asian pts who presented with AMI. Methods: A total 163 consecutive pts presented with AMI either ST elevation MI (STEMI) or Non-ST elevation MI (NSTEMI) between Oct 2004 and July 2006 were entered for analysis. Out of these 163 pts, 144 pts (88.3%) underwent PCI and 19 pts were not. Pts with documented MI with normal coronary artery was evaluated with acetylcholine (Ach) provocation test within two weeks of onset time. Results: A total 7 pts (7/163, 4.3%) with AMI (3 STEMI and 4 NSTEMI) with normal coronary artery were identified among the study population. Hypertension (5/7, 71.4%) was dominant among classic coronary risk factors. Female was common (5/7, 71.4%) and showed relatively younger age (45.8짹13.4 years). Mean ejection fraction was 42.7%짹10.6, showing mild left ventricular dysfunction and hypokinesis was the most frequent wall motion abnormality. Anterior wall (LAD territory) was the predilection location. Mean peak CK-MB was 73.9짹99.7 ng/ml, Troponin-T 2.67짹3.3 ng/ml, and BNP 1840짹2059 pg/ml. There was only one definite myocardial bridge in mid LAD (1/7, 14.3%) and three minimal fixed lesions (3/7, 42.9%) were observed. Incremental Ach provocation test showed significant vasospasm in 6 pts (6/7, 85.7%) and diffuse severe spasm (6/7, 85.7%) rather than focal spasm (1/7, 14.3%). Their clinical course was benign with antianginal medication and the incidence of hemodynamic complications and ischemic recurrences were not common up to 6 months. Conclusion: The incidence of AMI due to documented coronary vasospasm was 4.3% (7/163). Female, younger age and hypertension were prevalent. Ach provocation test confirmed the role of spasm and/or MB in the pathogenesis of AMI with normal coronary artery. LAD territory was the predilection site and mostly showed diffuse severe vasospasm. Clinical follow up up to 6 months showed favorable prognosis.