Background Aims: In this study, the effects of perfusion pressure, insulin, L-carnitine, propionate and 2,4-dinitrophenol on the utilization and oxidation of acetoacetate were investigated in the isolated nonworking perfused heart from normal and diabetic rats. Materials and Method: Hearts from Male Wistar albino rats were used. In the diabetic subgroup, Diabetes was induced by an intravenous injection of alloxan. The hearts were perfused at a perfusion pressure of 40 or 80 mmHg for 1 h with Krebs-Henseleit Medium, with the concentrations of calcium and magnesium halved, and oxygenated by equilibration with 5% carbon dioxide and 95% oxygen. Determination of acetoacetate and D-3-hydroxybutyrate levels were made by the method of Mellanby and Williamson and Williamson and Mellanby respectively, and comparison between groups was done using the twotailed Student's t-test for independent samples.