A total of 3409 cadavers was studied for changes of the internal mammary artery; sclerosis stenosis and occlusion of the vessel were quite exceptional. This fact is believed to be of importance from the aspect of myocardial revascularization by mammary-coronary anastomosis. Anastomoses were performed on cadavers; the vessels 1.5 to 2.5 mm in diameter were easy to suture.