Large losses of blood or plasma must be replaced. Increasing interest has been directed toward the use of noncolloid solutions for reexpansion of a depleted vascular compartment. Questions are raised regarding the effects of dilution and the volumes of electrolyte solution required to restore normovolemia after severe hemorrhage. In order to study this, splenectomized dogs were subjected to sequential 36%, 60%, and 75% hemorrhage, and rabbits to 70% plasmaphersis, with prompt infusion of a warm balanced salt solution. Note was taken of survival and hemodynamic parameters. Experiments Dogs: Hemorrhage.—The subjects were eight mongrel dogs, 8 to 15 kg (18 to 33 lb) previously subjected to splenectomy. Anesthesia was induced with intravenously administered pentobarbital, 25 mg/kg of body weight. The animals were intubated, but breathed room air spontaneously. A catheter was passed into the superior vena cava via the femoral vein. The femoral artery was similarly catherized, both pressures monitored