Clinical characteristics and coronary angiographic findings were analyzed in 24 patients with angiographically documented coronary artery spasm, which developed spontaneously in 11 cases and was provoked by intravenous ergonovine meleate in 13 cases. The commonest clinical presentation was chest pain at rest in 21 out of 24 cases, and nine patients with resting angina had also exertional chest pain. Ten patients complained of chest pain which developed especially at night and in the early morning. Cumulative doses of ergonovine meleate whoch were required to provoked spasm were 0.05mg in 3, 0.15mg in 8 and 0.35mg in 2 cases. Transient hypertension occured in one case as a complication of ergonovine provocation test. In 20 cases coronary artery spasm developed at the portion of normal or insignificantly narrowed coronary arteries, at the severely stenotic portion in 3 cases and at the normal portion different fropm severe tight lesion in one case. Electrocardiographic findings at the time of coronary spasm were ST segment elevation in 11 among 18 cases, ST segment depression in 2 cases and no change in 3 cases. Twenty two patients complained of chest pain of the same characteristics which they had previously experienced, but there was no chest pain in 2 patients. Right coronary artery was the most prevalent site of coronary artery spasm, and percutaneous transluminal coronary angioplasties were performes successfully in 4 cases with significantly tight lesions. In conclusion coronary artery spasm is thought to play a significant role in the conversion of stable to unstable angina and the development of silent myocardial ischemia as well as variant angina.