The hemodynamic changes associated with hemorrhagic shock have been well documented in animals and man. A relative paucity of information is available, however, concerning the alterations of hemodynamics occurring during "septic shock" in man. The administration of endotoxin to animals has demonstrated a fall in arterial pressure, a decrease in the circulating blood volume, and a reduction in the cardiac output. Although the assumption has commonly been made that similar changes occur in man, few data are available to confirm this. Udhoji et al1 have studied five patients with clinical shock associated with infection. They report a reduction in the cardiac index in these patients, although in one of their patients the cardiac output was in the high normal range. In two of their patients, the blood volume was normal or above normal. Ebert and Stead2 have demonstrated a normal blood volume in certain types of shock associated