Three models of disturbed erythrocyte metabolism, triose-depleted normal, phosphoglycerate kinase (PGK)-deficient, and pyruvate kinase (PK)-deficient cells, have been studied to examine further the role of PGK in erythrocyte cation transport. Sodium (Na-+) and potassium (K-+) transport were reduced only in cells fully depleted of triose. In such cells the PGK step presumably was inoperative due to total lack of substrate; 2,3-diphosphoglycerate (2,3-DPG) then became the sole substrate source for remaining steps in glycolysis. At increased intracellular Na-+ concentrations which normally stimulate transport and glycolysis, triose-depleted cells had marked impairment of cation transport and ouabain-inhibitable lactate and pyruvate production from 2,3-DPG. PGK-deficient cells and normal cells with high intracellular Na-+ concentrations had similar increases in transport and ouabain- inhibitable lactate production. PK-deficient cells with high intracellular Na-+ concentrations showed an appropriate increase in transport but less stimulation of lactate production. Transport was not related to total cellular adenosine triphosphate (ATP) concentration. These data suggested that normal coupled cation transport occurred despite diminished metabolite flow through PGK, as in PGK- or PK- deficient cells. Transport was diminished only in triose-depleted cells where metabolite flow through PGK was presumably absent. These data, therefore, support the concept that transport and glycolysis interact at the PGK step, although impairment of PGK must be profound before its effect on transport is eviden.