1. Plasma albumin concentration was measured in fifty-eight patients with chronic renal failure. The mean value was 3·27 g/100 ml (SD 0·44 g/100 ml; range 2·4–4·3 g/100 ml) which is significantly lower (P < 0·001) than normal (mean 3·94 g/100 ml; SD 0·23 g/100 ml; range 3·5–4·4 g/100 ml). In thirty-eight of the fifty-eight patients (65%), plasma albumin concentration was below the normal range. Treatment by maintenance haemodialysis or renal transplantation usually corrected the hypoalbuminaemia.
2. Radioactive iodine-labelled albumin turnover was investigated in twelve patients. Although plasma albumin concentration was reduced in eight of the twelve patients, the plasma half-life (T½) of the labelled albumin was normal or increased in all but one of these patients. Fractional and absolute albumin degradation rates (which include urinary albumin loss) were reduced in six of the twelve patients. In two of the four patients with normal plasma albumin concentrations the fractional albumin degradation rate was reduced.
3. Albumin synthesis was estimated by measuring the rate of incorporation into plasma proteins of 14C in two patients on a 20 g protein diet. The values were low in both.
4. Albumin catabolism and albumin synthesis were normal in two patients who had been on regular haemodialysis for 5 and 8 weeks respectively.
5. We conclude that these abnormalities in albumin metabolism were probably due to severe protein depletion, induced either by prolonged anorexia and vomiting or by deliberate restriction of protein in the diet in the course of treatment.