The present study was undertaken to determine the effect in rats of in vivo infusion of ATP MgCl2 on tissue insulin resistance in shock. The results indicate that insulin resistance can be overcome by the infusion of ATP MgCl2 to animals in shock. Although ATP levels in shock tissues increased following treatment, the relationship between ATP levels and insulin effect has yet to be established. It has been shown that cellular swelling occurs during shock, and it is also known that ATP induces muscle contractions. ATP induces membrane conformational changes. Whether the effect of ATP MgCl2 in overcoming tissue insulin resistance with shock is due to reversal of cell swelling or due to some other metabolic or membrane effect is not yet known.