1. Glomerular nitration, wate rconcentration and acid load tests, measurement of urinary protein and cell excretion rates, bacteriological examination of the urine, and analysis of the urinary amino acid content were carried out in eight patients with chronic intravascular haemolysis due to aortic valve replacement.
2. All results were normal except for a slight reduction in creatinine clearance rate in two patients and a slight elevation of urinary protein in a third; these abnormalities were considered of doubtful significance.
3. It is concluded that chronic intravascular haemolysis with its consequent renal haemosiderosis appears not to interfere with renal function.