Whole blood oxygen affinity, erythrocyte pH and organic phosphates were studied in five anaemic untransfused patients with end stage renal disease undergoing continuous ambulatory peritoneal dialysis. Decreased whole blood oxygen affinity with increased adenosine triphosphate and normal 2.3 diphosphoglycerate (DPG) values were observed. Normal and stable serum phosphate and permanent mild metabolic acidosis may be important factors contributing to maintain DPG levels within the normal range despite anaemia. Continuous dialysis avoids cyclic fluctuation of blood oxygen affinity as described during and after dialysis sessions in patients on maintenance haemodialysis.