BACKGROUND AND OBJECTIVES: The degree of coronary vasoconstriction induced by acetylcholine administeration can vary. We compared the prognosis between coronary vasospasm and intermediate vasoconstriction, which were both induced by acetylcholine administration. SUBJECTS AND METHODS: The subjects were 156 patients with the coronary vasospasm or intermediate vasoconstriction, as observed on the acetylcholine provocation tests that were performed from January, 2000 to January, 2004. The patients with a spasm showing greater than 90% reduction of vessel diameter along with chest pain or ST changes or both were classified as having 'strong positive vasospasm' (n=113). The patients with 70-90% reduction of diameter were classified as having 'intermediate vasoconstriction' (n=43). The mortality, frequency of chest pain and clinical events were then analyzed. RESULTS: A smoking history (p<0.001) and multivessel involvement (p=0.02) were more frequent in the strong positive group. We compared the mortality and clinical events due to chest pain during the average 26.4+/-14.1 months of follow-up. There were 5 patients (4.4%) who incurred cardiac death in the strong positive group as compared with none in the intermediate group. The total clinical events were more frequent in the strong positive group (p<0.001). Also, the strong positive group showed a significantly higher frequency of chest pain (p<0.001). CONCLUSION: The long-term prognosis of the intermediate vasoconstriction was better than that of strong positive vasospasm. Thus, the intermediate vasoconstriction must be ruled out by strict application of the positive criteria for the acetylcholine provocation test.