Background: The clinical and angiographic characteristics of coronary artery spasm (CAS) have been known to be different between Japanese and Caucasian population. However, the angiographic characteristics in patients with significant CAS in a series of Korean population are not clarified yet. Methods: We performed intracoronary Acetylcholine (Ach) provocation tests in 1,027 Korean patients (pts) presented with typical or atypical chest pain from November 2004 to June 2007. 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 >70%. Results: A total 587 (57.2%) pts showed positive Ach provocation tests. The positive pts were significantly older (55.5짹11.1 vs 51.8짹13.1, P<0.01), hypertensive (45.5% vs 33.0%, P<0.01), hyperlipidemic (17.4% vs 8.4%, P<0.01) and more smoker (25.9% vs 19.1%, P<0.05) compared with those of the negative pts. The positive pts showed higher baseline spasm rate (46.3% vs 25.0, P<0.01). Although most of positive pts did not show EKG change (89.4%), but more than half of pts experienced chest pain (61.8%) during the test. Most positive pts needed higher dose of Ach to induce CAS, more diffuse CAS and more single vessel spasm. Characteristically, some positive pts had fixed lesion (mixed angina) and myocardial bridge (MB, Table). Conclusion: Advanced age, hypertension, hyperlipidemia and smoking might be the major risk factors of CAS. Furthermore, positive test pts showed more spastic at baseline, needed higher Ach dose and more diffuse type in single coronary artery. Only 1/3 had combined MB and 12% showed mixed angina.