Typically, patients afflicted with syndrome X complained of stress induced angina pectoris, and their electrocardiograms show corresponding ST-segment depressions during exercise. However, angiography is unable to demonstrate significant coronary artery luminal narrowing and significant coronary artery spasm to provocation test. And left ventricular performance at rest remains remarkably unimpaired. Syndrome X is characterized by reduction of coronary vascular reserve but without depression of left ventricular performance or negative effect on survival. The reduction of coronary vascular response is supposed to be resulted from reduced coronary vasodilator reponse due to abnormal contraction of coronary prearteriolar vessels. This case is a 43-year-old female who has had exertional chest pain since 5 months ago. The chest pain was relieved by rest and subligual nitroglycerin administration. The exercise electrocardiography showed significant ST segment depressions on lead II, III aVF and V₄-V₆ at stage 1, when she experienced chest pain. On 24 hour ambulatory electrocardiogram, significant ST segment depression was recorded at the time when the patient had chest pain. But coronary arteriography demonstrated normal coronary artery and no significant coronary artery spasm to provocation test with ergonovine maleate. On exercise thallium-201 scintigraphy, perfusion decrease was suspected on anterolateral wall of left ventricle. The patient was diagnosed as a syndrome X and was managed with isosorbide and nifedipine and her exercise tolerance increased significantly on follow up exercise test performed 1 month later. But she has complained of a few of attack of chest pain until now.