To evaluate the relationship between myocardial perfusion and fatty acid metabolism in canine myocardial infarction, 16 dogs were studied using thallium and 123I-beta-methyl-iodophenyl pentadecanoic acid (BMIPP). Eight dogs (group A) had left anterior coronary arterial occlusion (6 h ligation), 6 dogs (group B) had reperfusion (3 h ligation and 1 h reperfusion) and 2 dogs served as the normal control. Myocardial imaging with BMIPP was excellent, owing to its higher uptake and longer retention in myocardium and rapid blood disappearance in addition to diminished liver and lung uptake. The mean half time value which was generated from the BMIPP myocardial washout curve, was significantly larger in the reperfused myocardium. The gamma camera imaging showed uncoupling of BMIPP and thallium (BMIPP uptake greater than thallium uptake) in five dogs in group B. On the other hand, all dogs in group A had a persistent defect in BMIPP and thallium uptake. Our findings indicate that the combination of BMIPP and thallium for myocardial imaging supply different information about the zone of infarction and ischemia, which may be useful for the assessment of myocardial viability.