In patients with diabetes mellitus, the existence of diabetic cardiomyopathy was substantiated. This study was undertaken to evaluate the myocardiac fatty acid metabolism of diabetic mice (n = 21) and controls (n = 21) in 125I-BMIPP in fasted and unfasted states. 125I-BMIPP of 370 kBq was given and thirty minutes later, animals from both groups were killed. Samples of hearts, liver and other organs were removed, weighed and then counted in a scintillation counter. The percent injected dose/g of hearts of diabetic mice was significantly reduced compared to controls in unfasted (p < 0.05) and fasted (p < 0.01) groups. These findings may reflect impaired fatty acid utilization of the hearts in diabetic mice compared to controls.