We report a case of 34-year-old woman who had left main coronary artery disease and treated with medication only. She was presented with severe chest pain. Isolated left main coronary disease was demonstrated on selective left coronary angiography. There was no regional wall motion abnormality on echocardiogram with normal global LV systolic function. We considered the lesion as a varient of Takayasu's arteritis. So with anti-anginal medication, treatment started with steroid therapy. After then there was no chest pain. We performed follow-up coronary angiography after 1 month and 3 month in which revealed improved left main lesion. Since then there was no subjective symptom and Thallium-201 SPECT revealed no significant ischemic finding. We think that this case's underlying disease is may be Takayasu's arteritis which has isolated left main stenosis without systemic involvement and improved with medical treatement only.