A singular scheme of progressive alterations in cell function with hemorrhagic shock and ischemia has been presented. Alterations in mitochondrial function during shock and ischemia with different substrates have been described in detail. These consist of decreases in the capability of mitochondria, alterations in mitochondrial cation contents, increased mitochondrial FFAs and Ca2+ levels, and decreased adenine nucleotide translocase activity. The potential mechanisms responsible for altered mitochondrial functions during shock and the potential consequences of such alterations have been discussed. In addition, the beneficial effects of ATP-MgCl2 on mitochondrial function following shock and ischemia have been described. The experimental evidence available indicates that infused ATP-MgCl2 improves cellular and mitochondrial functions directly and by way of long-term improvement in microcirculation but not through vasodilatation. Our results with ATP-MgCl2 therefore provide for the possibility of supporting cellular and mitochondrial functions during shock or low flow conditions.