Loss in mitochondrial function and induction of mitochondrial-mediated apoptosis occur as a result of cardiac ischemia/reperfusion. Brief and repeated cycles of ischemia/reperfusion, termed ischemic preconditioning, prevent or minimize contractile dysfunction and apoptosis associated with prolonged episodes of cardiac ischemia and reperfusion. The effects of preconditioning on various indices of ischemia/reperfusion-induced alterations in mitochondrial function and structure were therefore explored. Utilizing an in vivo rat model data is provided indicating that preconditioning completely prevents cardiac ischemia/reperfusion-induced: (1) loss in the activity of the redox sensitive Krebs cycle enzyme alpha-ketoglutarate dehydrogenase; (2) declines in NADH-linked ADP-dependent mitochondrial respiration; (3) insertion of the pro-apoptotic Bcl-2 protein Bax into the mitochondrial membrane; and (4) release of cytochrome c into the cytosol. The results of the current study indicate that preconditioning prevents specific alterations in mitochondrial structure and function that are known to impact cellular viability and provide insight into the collective benefits of preconditioning.