Over a 50-year period from the first description of Kawasaki disease, we encountered three male patients with a history of Kawasaki disease, who had their first cardiac events in their forties. They were considered to have almost normal coronary arteries in the coronary angiograms when they were children and adolescents. They had no follow-up examinations after 20 years old. The 1st patient had an acute myocardial infarction, and the 2nd was a new appearance of coronary aneurysm and stenotic lesions with coronary artery calcification. The 3rd patient had unexpected sudden death. The interval from the onset of Kawasaki disease to the cardiac events ranged from 37 to 38 years. In the former two patients, coronary artery lesions could not be evaluated immediately after Kawasaki disease. Although the 3rd patient had bilateral medium-sized coronary artery aneurysms, his coronary aneurysms regressed 1 year after acute Kawasaki disease. The intimal thickening at a previous coronary aneurysm at the age of 19 was mild. The patients with regressed coronary aneurysms were asymptomatic for about 40 years after Kawasaki disease, prior to their cardiac events. Coronary artery calcification of the proximal portion of the major coronary arteries was a predictable marker in such patients. To prevent serious cardiac events in middle-aged adult patients, reevaluation of coronary artery lesions and restarting of anti-thrombotic therapy are needed. We must be aware that there are some differences in the clinical course and time of cardiac events between patients with giant aneurysms and those with medium aneurysms.