The uptake of technetium-99m stannous pyrophosphate in contused myocardium was measured as a function of time from the insult. The free wall of the dog's left ventricle was surgically exposed and struck with a spring-loaded paddle. Pyrophosphate was injected intravenously from 1 1/2 to 47 1/2 hr after the injury. After 1/2 hr of incubation the hearts were removed and the Tc-99m content of contused and noncontused myocardium was measured. Pyrophosphate was concentrated in contused myocardium at all of the time periods tested. Contused-to-normal ratios for pyrophosphate uptake ranged from 8.1 (8 hr) to 41.9 (48 hr).