To determine whether normal exercise images can reduce the need for coronary arteriography, we analyzed our data on 102 patients with normal thallium 201 exercise images who underwent coronary arteriographic studies. Eight-two patients had normal or insignificant coronary artery disease; 20 patients had significant coronary artery disease. Eight patients had disease limited to one of the secondary branches of the left system; seven patients had disease limited to one of the major coronary arteries; two patients had disease involving the right coronary artery and a secondary branch; two patients had disease involving two secondary branches; and one patient had disease involving the three major vessels. Seven of the 20 patients had abnormal exercise ECGs, and the remaining 13 patients had normal or inconclusive exercise ECGs. Our findings indicate that significant coronary artery disease is rare in patients with normal exercise images, especially if patients with abnormal exercise ECGs are excluded. Thus, normal exercise images could possibly reduce the need for coronary arteriography, since in these patients coronary artery disease rarely requires bypass surgery.