Many people have suffered from atherosclerosis. It is now known to be caused by chronic inflammation of autoimmune-like disease. In order to elucidate the mechanism of atherosclerosis, it is showed that the atherosclerotic changes in 44 biopsy specimens of media of the ascending aorta associated with coronary artery disease and have reported that aortas of coronary-diseased patients increasing of infiltration of plasma cells and mucoid degeneration. In atherosclerosis, autoimmune reaction occurs at the mild to moderate atherosclerosis, at the same time sulfated bile acid and some bile acids increase. In post-autoimmune reaction, sulfate bile acid increase again. Sulfated bile acid may possibly be main cause for atherosclerosis.