To clarify whether the cardiac sequelae of Kawasaki disease (KD), postcoronary arteritis lesions can become a risk factor for atherosclerosis of the coronary arteries, six autopsy cases of patients older than 15 years of age with coronary arterial lesions caused by arteritis in childhood were examined histologically. Twenty-four arteries were inspected: 10 had no evidence of aneurysm formation, 7 arteries manifested simple dilatation of the lumen, and in 7 arteries there were aneurysms with recanalization. In the group in which there were no aneurysms, "new intimal thickening" was observed in addition to the preexisting intimal thickening which had been caused by arteritis in the acute phase of KD. In the second group with aneurysmal arteries whose lumen remained dilated, thrombotic occlusion occurred in 4 of 6 aneurysms. In addition, advanced atherosclerotic changes (i.e., complicated lesions) were found in a 39-year-old patient. Finally, in the third group of arteries which manifested recanalized lumens after thrombotic occlusion of the aneurysms, new intimal thickening was seen on the internal side and some of them were occluded. The findings in this study suggest that aneurysms present in coronary arteries in individuals with a history of KD constitute a risk factor for atherosclerosis later in life.