Hormonal regulation is fundamental to homeostasis, and the response in tissues is mediated by adenosine 3':5' equals cyclic phosphate (cyclic AMP). Since circulating levels of catecholamines are elevated during hemorrhagic shock, experiments were carried out to study the effects of epinephrine and of shock on cyclic AMP levels of plasma and of the intestine, a particularly vulnerable organ in canine hemorrhagic shock. Epinephrine was given to normotensive dogs as a constant infusion (group 1) or as a single pulse (group 2). Sequential blood samples showed a marked increase in circulating cyclic AMP, especially in portal and hepatic venous blood. Little change was noted in the tissues. Hemorrhagic shock (group 3) induced a marked increase in plasma cyclic AMP, with a depletion of mucosal cyclic AMP and adenosine triphosphate (ATP). Pretreatment before shock with alpha-blockade (group 4) abolished the decrease in mucosal cyclic AMP and ATP, and reduced the increase in plasma cyclic AMP.