Hypovolemic shock remains a lethal complication of injury and surgery, frequently accompanied by multisystem organ failure. We have shown that visceral organ blood flow remains markedly depressed for 18 hours after apparently successful resuscitation from shock. Recent work by others and studies by us have demonstrated a significant increase in survival after hemorrhagic shock in rabbits treated with antiserum to E. coli J5. We postulate that severe shock enhances endotoxin absorption from the gut and impairs the ability of the reticulo-endothelial system to clear endotoxin from the portal system. This results in spillover of endotoxin to the systemic circulation. Systemic endotoxemia in severe hemorrhagic shock may contribute to immediate mortality to later problems with multiple systems organ failure and to the observed prolonged abnormalities in visceral blood flow. We propose a series of experiments to 1) confirm the dramatic improvement in survival with antiendotoxin treatment of animals in hemorrhagic shock, 2) to investigate changes in visceral organ function and regional blood flow in shock animals with and without antisera treatment, 3) to verify and further characterize these findings in another larger species, primates. We believe we have discovered an important factor contributing to post resuscitative morbidity and mortality in severe hemorrhagic shock and these experiments are intended to confirm or reject these beliefs.