Cation flux and the extracellular and erythrocyte concentrations of sodium, potassium, calcium, magnesium, chloride, and acid soluble phosphorus were measured in fresh blood collected in various anticoagulant solutions, ACD blood stored at 4 C, and in frozen-deglycerolized blood stored at -80 to -120 C. Considerable variations in concentrations of extracellular and erythrocyte electrolytes were encountered due to certain characteristics of the anticoagulants employed and to the effects of storage, temperature, pH, and extracellular electrolyte concentration on erythrocyte electrolyte concentration. In contrast to ACD blood stored at 4 C, frozen-deglycerolized blood 1 day to 32 months old had slightly elevated erythrocyte concentrations of sodium and chloride and normal erythrocyte concentrations of potassium and phosphorus. Both ACD and frozen-deglycerolized blood had normal sodium and potassium fluxes. These data show that prolonged freezing and glycerolization of erythrocytes do not significantly impair the active transport processes responsible for maintenance of cellular electrolyte concentration.