We examined the extent to which ischemic myocardium was salvaged by reperfusion using a method that allowed expression of the volume of infarction as a percentage of the volume of the perfusion bed of the occluded artery (region at risk of infarction). In eight baboons, the left anterior descending coronary artery (LAD) was occluded for 2 hours, after which perfusion was restored. A control group of eight baboons underwent an identical protocol, but perfusion was not restored. Twenty-four hours after occlusion, microvascular dyes were injected into the LAD and adjacent arteries to delineate the perfusion bed of the occluded artery. The volume of infarction and volume of the perfusion bed were determined planimetrically. The mean percentage of the perfusion bed infarcted in the control baboons was 94.2 +/- 3.5% and 50.1 +/- 5.8% in the reperfused baboons. Hence, the mean percentage of the perfusion bed infarcted was reduced by 44.1% in the reperfused group compared with the control group (p less than 0.001). In reperfused baboons, hemorrhage occurred in the region of infarction but did not result in infarct extension. We conclude that reperfusion after 2 hours of coronary occlusion results in substantial salvage of ischemic myocardium in the baboon.