AbstractAbnormal vascularity in the region of the left atrial appendage was demonstrated by coronary arteriography in 5 patients with mitral stenosis. Subsequently, three of these patients proceeded to operation, and left atrial thrombi were confirmed in all three cases. Neovascularity must be differentiated from congenital fistulae, tumours, and coronary artery disease. Thrombus in the left atrial appendage is difficult to diagnose even with the use of cross‐sectional echocardiography and may occasionally be demonstrated by coronary arteriograph