The present study was undertaken to establish the time limit until the beginning of reperfusion that would permit restoration of contractility in acute myocardial infarction, and to confirm the delayed recovery of dyskinesis in ischemic area followed by reperfusion. Studies were carried out in 31 dogs of which 29 had temporary (20 min to 5 hours) occlusion of the left anterior descending coronary artery with short or long term reperfusion, and 2 had permanent occlusion. Dyskinesis was detected with tension curve obtained using a strain gauge arch. In the short term reperfusion study, dyskinesis disappeared if reperfusion was begun within 20 min of ischemia. However, dyskinesis remained after one hour of reperfusion, if reperfusion was done after 40 min of ischemia. Reperfusion for 10 days after 3 and 4 hours of occlusion resulted in recovery of regional myocardial contractility. However in 2 of 5 animals with 5 hours of coronary occlusion, the reperfused area remained dyskinetic even after 10 days of reperfusion. It is concluded that revascularization of myocardium that had been kept ischemic for less than 4 hours may lead to disappearance of dyskinesis. These findings also indicate that early coronary revascularization doses not always provide an immediate recovery of dyskinesis of the revascularized area.