To elucidate 1-carnitine chloride effects ischemic myocardium for the possibility of a salvage of risk zone around necrosis in myocardial infarcts of dogs, a quantitative evaluation of the extent of myocardial infarcts was done by size detection with use of monastral blue and tissue dehydrogenase histochemistry at 20 hours after coronary ligation. The results show that the ratio of unsalvaged infarct zone to occluded coronary bed is 85.3 +/- 2.9% in the control group, while it is 53.2 +/- 3.6% in the 1-carnitine administered (1 C) group. The difference between these ratios is statistically significant (p less than 0.01). The results also indicate significantly lower serum CPK concentration. Therefore, carnitine may play a role in preventing a size extention of infarcts through improving an altered lipid metabolism, particularly a fatty acid metabolism, of myocardial cells in the risk zone.