Arteriographic findings of neovascularity and fistula formation between coronary arteries and left atrium have occasionally been described in association with left atrial thrombosis in patients with mitral valve disease. The validity of these coronary arteriographic findings in diagnosis of atrial thrombi has been evaluated in 164 patients with mitral valve disease. Comparison was made with surgery. The study provided these diagnostic values: sensitivity 65%, specificity 85%, positive predictive value 72%. Even if this angiographic finding is complementary in diagnosis of atrial thrombosis, its identification during coronary arteriography in patients with mitral valve disease is useful. Its detection could improve diagnostic prediction of thrombosis especially in patients without previous embolic events or where echocardiography failed to show thrombi.