According to our results the long-term daily oral supplementation of 6 mg vitamin B6 was sufficient for prevention of vitamin B6 deficiency in chronic renal failure, regular dialysis treatment and CAPD groups of patients. Haemodialysis and charcoal haemoperfusion have led to non-significant decrease of erythrocyte vitamin B6. A favourable effect was found of daily oral administration of 50 mg pyridoxine on electrophoretic mobility of peripheral blood lymphocytes and cellular immunity.