In this report, we describe the clinical, hemodynamic, and angiographic findings in three patients with atherosclerotic complete occlusion of the left main coronary artery. This rare entity was only seen in three out of 7,000 coronary angiograms. The three patients had extensive right-to-left collateralization. Two patients underwent saphenous vein bypass surgery and are asymptomatic, while the third patient died awaiting surgery. We suggest that patients with complete left main occlusion must undergo surgery as soon as possible. © 1979.