When administered in sufficient amounts, normal saline and Lactated Ringer's Solution are equally effective in maintaining adequate circulatory volumes despite severe blood loss and resultant hypoproteinemia. Arterial pH is maintained within normal limits when either solution is used for resuscitation provided the circulatory volume has been re-expanded to adequate levels for good tissue perfusion and support of aerobic metabolism. The pH of the infused solutions has no effect on blood pH under these circumstances. Fourteen splenectomized dogs were subjected to continuous hemorrhage and simultaneous replacement with either normal saline or Lactated Ringer's Solution. The cumulative replacement volume ratio necessary for equilibration after 61% RBC depletion was 7:1 crystalloid to the whole "undiluted" blood shed, in both groups. Indicators of pulmonary-circulatory physiology remained stable within normal limits. Arterial pH did not exhibit significant changes from normal values after resuscitation with NS or LRS. The group infused with LRS exhibited no change in arterial pH, 7.40 plus or minus .07 initial and 7.40 plus or minus .09 final; in the group with NS replacement a slight decrease from control was noted, 7.40 plus or minus .07 initial and 7.36 plus or minus .06 final. These differences, however, are not statistically significant. Of the 14 subjects, 13 were long-term survivors. The one death was associated with a technical mishap shortly after completion of the experiment. Because banked blood imposes a "net" alkaline metabolic load (sodium citrate), patients expected to be transfused with large volumes of stored blood might be better resuscited with normal salin than with Ringer's Lactate Soultions, to minimize or avert the otherwise resultant metabolic alkalosis.