Of 278 patients undergoing aorto-coronary artery bypass grafts through July 1970, a total of 167 (62.2%) had 220 complete occlusions of one or more major coronary arteries. The right coronary artery (RCA) was occluded in 61%, the left anterior descending (LAD) in 28%, the left circumflex (LCA) in 10%, and the left main (LM) in less than 1%. Previous myocardial infarctions, congestive heart failure, incapacitation, and elevated left ventricular end diastolic pressure were more common in this group than in those with stenotic lesions. The RCA was most often suitable for bypass graft, followed by the LAD, and lastly the LCA. In the small group without demonstrable distal collaterals on arteriograms, distal bypasses were done successfully beyond 70% of the occluded RCAs, 51% of the LADs, and none of the LCAs. Operative mortality (30 days) was only 3% higher in the occluded than in the stenotic group. Postoperative angiographic patency rates were the same.