In order to determine whether plasma iron becomes elevated in other forms of experimental shock as it does in hemorrhagic shock, plasma iron was measured in rabbits subjected to lethal doses of endotoxin or infused with lethal amounts of catecholamines, and in dogs in superior mesenteric artery (SMA) occlusion shock. Patterns obtained from these animals were compared with those obtained from rabbits and dogs shocked by hemorrhagic hypotension. In both species hemorrhagic hypotension caused marked elevations in plasma iron, while iron levels were depressed in rabbits treated with endotoxin or lethal infusions of catecholamines and in dogs in shock following SMA-occlusion. The implications of these observations are discussed with respect to differences in tissue oxygen supply in normovolemic and hypovolemic forms of shock and with respect to the presumed role of hyperferremia in the vasculotoxic sequelae of the shock syndrome.