The topographic relationship between the uptake of technetium-99m pyrophosphate (PPi) and myocardial infarction delineated by 2,3,5-triphenyl tetrazolium chloride (TTC) was studied in a canine model of permanent coronary occlusion (24-48 hr). Photographs of TTC staining and scintigraphic images of PPi uptake were planimetered for infarct area. In addition, narrow tissue samples (3 X 10 mm) were taken on both sides of the TTC border and counted for PPi uptake. A significant correlation (p less than 0.001) was found between area of PPi uptake and area of myocardium unstained by TTC (r = 0.84 in epicardium and r = 0.91 in endocardium). The slope relating PPi to TTC for all infarcts was 1.01 +/- 0.11, indicating that variations in infarct size were followed equally by the two techniques. Tissue counting showed the ratio of PPi activity just inside the infarct to activity just outside the infarct to be 9.2 +/- 0.6 (mean +/- s.e.m.). Thus, PPi is distributed topographically in a manner identical to the distribution of irreversibly injured myocardium as delineated by TTC.