In 62 men with open parent coronary arteries who underwent saphenous vein aortocoronary bypass to either the right or left anterior descending coronary artery, or both, left ventricular ejection fraction and wall motion of the anterior and inferior segments of the left ventricle were measured before and after (average 11 months) the operation. Of 34 left ventricular segments with open vein grafts and open parent coronary arteries, 91 percent were unaltered by the operation, none were in worse condition and 9 percent showed improved wall movement. Among 33 segments with open grafts but new total occlusion of the parent coronary arteries, 67 percent were unaltered, whereas the condition of 18 percent was worse and of 15 percent was improved. Among 21 segments with closed grafts but patent parent arteries, the condition of 29 percent was unchanged and of 71 percent was worse; among 14 segments with occlusion of both grafts and parent arteries the condition of 29 percent was unchanged and of 71 percent was worse. In 10 men with patency of all vein grafts and parent arteries, left ventricular ejection fraction was not altered (0.55 +/- 0.03 to 0.53 +/- 0.04 [average +/- standard error of the mean]) and in 11 with all grafts open but all parent arteries occluded left ventricular ejection fraction was unchanged (0.51 +/- 0.02 to 0.54 +/- 0.03). Left ventricular ejection fraction was decreased in eight men with occlusion of all vein grafts whether or not occlusion of the parent coronary arteries had occurred. The results suggest that occlusion of the parent coronary arteries in the presence of a patent vein graft does not unfavorably alter left ventricular ejection fraction or segmental wall motion, whereas graft occlusion is associated with deterioration of left ventricular ejection fraction and segmental motion whether or not the parent artery is also occluded.