Evidence of mitochondrial dysfunction in diabetes led us to examine whether diabetes altered the nature of the mitochondrial permeability transition. Our data reveal three diabetes-associated abnormalities in PT function: consistently delayed induction with calcium-phosphate, a variable delay with calcium-t-butyl-hydroperoxide (t-BuOOH), and an enhanced magnitude of response. The consistently delayed induction in calcium and phosphate is correlated with serum glucose levels, and is consistent with known changes in calcium uniporter function in diabetics. These data expand our knowledge of diabetes-associated abnormalities in mitochondrial function, represent the first evidence that the PT is altered by chronic disease, and provide potential partial mechanistic explanations for the previously observed resistance of diabetic tissues to ischemia-reperfusion injury and the altered Ca2+ homeostasis in diabetics.