In a group of 69 patients with chronic renal failure, 18 patients after renal transplantation and 8 healthy controls the influence of inorganic phosphate and pH of plasma and of the hemoglobin concentration in whole blood on the 2,3-DPG concentration in red blood cells was investigated. The data were treated by linear regression analysis as well as by multivalent correlation analysis with graph-theoretical methods. Hemoglobin and inorganic phosphate are the factors of renal importance for the 2,3-DPG concentration. The pH affects 2,3-DPG directly (positively) and indirectly via inorganic phosphate (negatively). Therefore, the influence of pH on 2,3-DPG usually observed is abolished in this group of patients. Determinations of inorganic phosphate and hemoglobin seem to be valuable for the diagnosis of the 2,3-DPG-dependent oxygen transport function during chronic renal failure. All the parameters studied were found to be normalized in the group of patients after renal transplantation.