A coronary artery and the accompanying vein were ligated temporarily for 30, 60 and 120 minutes in 39 cats. By labelling the blood with the fluorescent dye acridine orange, the intravital blood supply of the myocardium was investigated 5 minutes to 6 hours after release of the ligature. The region supplied by the temporarily ligated coronary artery (RSCA) was demonstrated by postmortal perfusion of this vessel using the dye light green. Resumption of circulation in the deeper layers of the RSCA was delayed after a prior coronary occlusion, even occasionally after occlusions lasting only 30 minutes. After a coronary ligation of 60 to 120 minutes the inner layers of the RSCA became the sites of prolonged disturbance of blood supply. The circulatory abnormality observed immediately following release of the ligature did not result from intraluminal vascular obstruction. Even after a temporary ischemia lasting 120 minutes it was still possible, immediately after removal of the ligature, to perfuse an intravitally ischemic portion of the RSCA. The significance of these results for the determination of the so-called "revival-time" of the cardiac muscle is pointed out.