Background: Vasodilators are usually temporally stopped before the intracoronary acetylcholine (ACh) provocation test, a widely used method for detecting vasospastic angina. However, little has been known about the impact of temporal cessation on coronary artery spasm (CAS) as assessed with this method. Methods: A total of 1199 patients (pts) presented with chest pain underwent coronary angiography were enrolled. Acetylcholine was injected into left coronary artery in incremental doses of 20關g/ min, 50關g/ min and 100關g/ min. Vasodilators were withheld 3 days before the test. Significant CAS was defined as a transient > 70% luminal narrowing with concurrent chest pain and/ or ischemic ST-segment change. Results: After 3-day cessation, pts treated with nitrates, nicorandil, diatiazem and/or molsidomine had significantly higher incidence of CAS than those without previous treatment (P<0.001). There was a trend toward significantly higher incidence of CAS in pts who stopped other calcium channel blockers (CCB) for blood pressure control (35.6% vs 29.2%, P=0.055). The incidences of CAS in pts who stopped angiotensin converting enzyme inhibitors (ACEI), angiotensin receptor blockers (ARB) and beta-blockers were similar to those in pts without previous treatment. Multivariate logistic analysis showed that the cessation of nitrates, nicorandil and diltiazem was significantly associated with the higher incidence of CAS, whereas, the cessation of beta-blockers was associated with reduced CAS. The cessation of other CCB, ACEI, ARB and trimetazine did not significantly influence on the incidence of CAS. Conclusions: The temporal cessation of antianginal agents for 3 days was independently associated with higher incidence of CAS. Therefore, the cessation of antianginal agents should be cautious, and the confounding effect of vasodilator should be taken into account when we perform the ACh provocation test.