In order to assess zinc status in patients with chronic renal failure (CRF) plasma and erythrocyte zinc levels were determined in 13 patients undergoing regular haemodialysis. Additional determinations of plasma copper, plasma and erythrocyte magnesium and potassium were also performed. The mean plasma zinc level was slightly less than normal, but the difference was not statistically significant. The erythrocyte zinc content, however, as well as erythrocyte magnesium and potassium levels were significantly increased (p less than 0.001). This increase may be partly related to haemolysis in uraemia. Plasma copper concentration in CRF patients did not differ significantly from the control level. The almost normal plasma zinc concentration, elevated erythrocyte zinc, and normocupraemia do not indicate zinc deficiency in CRF patients.