Myocardial cell death due to infarction is accompanied by an influx of calcium ion. The calcium ion seems to localize in crystalline structures that form within mitochondria and resemble hydroxyapatite. Based on this phenomenon 99mTc-stannous pyrophosphate has been successfully used to image myocardial infarcts within 24 hr of infarction and 1 hr following tracer administration both in dogs and patient volunteers. In this report, canine distribution studies of 99m-Tc-pyrophosphate are compared with similar studies with 99mTc-stannous polyphosphate, 99mTc-stannous 1, hydroxy-ethylidene-1, 1-disodium phosphonate diphosphonate), and 18F as sodium fluoride. Pyrophosphate polyphosphate, and diphosphonate are each potentially useful in myocardial infarct imaging but bone uptake of 18F occurs sufficiently early to prevent the use of this radionuclide in infarct scintigraphy.