We present the case of a 3 month old male Japanese infant who developed a myocardial infarction a month after the onset of Kawasaki disease. An electrocardiogram showed abnormal Q waves in leads V1 through V4. He was referred to our department eight days after the onset of myocardial infarction. Echocardiography on admission revealed giant left coronary aneurysms with massive thrombus in the lumen. Therapy with intravenous urokinase (5000 U/kg three times daily), heparin, and oral warfarin for one week failed to induce thrombolysis. A coronary angiogram revealed that a large thrombus occluded much of the lumen of the left …