The regional myocardial distribution of 99mTc-glucarate was compared to 3H-deoxyglucose in 22 rabbits with left circumflex marginal artery occlusion. In 12 rabbits, tissue radioactivity measurements were compared to the results of triphenyl tetrazolium chloride staining and light microscopy. In 10 additional rabbits, the myocardial sodium space (24NaCl), an indicator of tissue edema induced by injury, was compared to the distribution of deoxyglucose and glucarate. Technetium-99m-glucarate accumulated in injured myocardium within 6 hr after coronary ligation and myocardial concentration was greatest in the most severely injured zones (TTC unstained). Hydrogen-3-deoxyglucose behaved as a marker of ischemia but concentrated in tissue with injury ranging from mild ischemia (TTC stained) to transmural infarction (TTC unstained). Both 99mTc-glucarate and 3H-deoxyglucose concentrated in acute, severely injured myocardial tissue. These studies suggest that 99mTc-glucarate is a useful tracer for evaluating myocardial injury. In addition, it appears that 99mTc-glucarate and 3H-deoxyglucose demarcate different points in the spectrum of myocardial injury.