Limits of the supply area of the three large coronary arteries (right, left descending and left circumscribed branches) were determined by post-mortem angiography of 400 human hearts. The largest variation was demonstrated in the region of the posterior ventricular wall and the apex. Most frequently the border of the supply region between right and left circumflex branches extended across the middle of the left posterior wall. Hearts in which the left ventricular posterior wall was supplied from both right and left circumflex branches (normal type) constituted 82% of all cases. In the right-coronary dominant type (10%) the left ventricular posterior wall, at least at the base, was supplied by the right coronary artery, while in the left-dominant type (8%) the right coronary artery did not supply any part of the left posterior wall. At the apex the left descending branch rose dorsally by about 0.2-5.0 cm in 70% of cases, while the posterior interventricular branch only rarely supplied the apex (1.1%). The left coronary artery showed most variations in the anterior wall. It divided into two in 41%, into three with an additional diagonal branch in 53% and into four in 6%.