Background: Coronary arteriovenous fistula (AVF) is a rare coronary anomaly and can be responsible for myocardial ischemia due to a ���steal syndrome���. However, its incidence in Asian population, association with significant coronary artery spasm (CAS) or microvascular dysfunction is largely unknown. Methods: Study population consisted of 6,010 patients (pts) underwent diagnostic coronary angiography (CAG) between Sept 2004 and Aug 2007. In selective pts who had coronary AVF undewent intracoronary Acetylcholine (Ach) provocation tests for assessing the combined significant CAS. Incremental Ach doses of 20, 50 and 100 (A1-A3) µg was given into the left coronary artery. Significant CAS was defined as transient luminal narrowing >75%. We assessed overall incidence of coronary AVF, its association with CAS, microvascular dysfunction or combined other coronary anomalies. Results: The overall incidence of coronary AV fistula found during the diagnostic CAG was 0.28 % (17/6,010 pts). Mean age of 17 pts with coronary AVF was 50.7 짹 13.6 years and male was in 52.9% (9/17). Two pts had two 3 separate AVF, two pts had 2 separate AVF and rest of 13 pts had single AVF. The predilection origin sites were 10 in left anterior descending artery (LAD), 9 in right coronary artery (RCA), 2 in left main (LM), 1 in left circumflex artery (LCX) and 1 diagonal branch. The usual drain sites of AVF were to pulmonary artery, right ventricle or atrium. Twelve pts (70.6%, 12/17) underwent Ach provocation test and 7 pts (58.3%, 7/12) showed significant CAS. Six pts (50%) showed very spastic appearance on baseline angiography. Most of the pts showed diffuse severe spasm instead of single vessel focal spasm. Two pts (16.6%) had combined myocardial bridge in the mid LAD, two pts had coronary aneurysm in RCA and one pt had focal coronary ectasia. Conclusion: The incidence of coronary AVF in a series of Asian population was approximately 0.3% and more than half of the pts showed significant CAS on Ach provocation test. The CAS pattern was diffuse severe multivessel spasm and pts with AVF infrequently combine other congenital coronary anomalies including coronary aneurysm and ectasia.