A 23-year-old man with homozygous familial hypercholesterolemia was found to have coronary ectasia by coronary angiography. This case showed generalized xanthomatosis and severe hyper low density lipoproteinemia, and his cultured skin fibroblasts showed LDL receptor activities compatible with the receptor-defective homozygous type of familial hypercholesterolemia. Coronary angiography showed fusiform aneurysmal involvements in the right coronary artery and left circumflex artery, and 50% stenosis in the right coronary artery and left anterior descending artery. Thus, homozygous familial hypercholesterolemia produces coronary ectasia as well as premature coronary stenosis.