1. The haemolytic complications of Starr—Edwards ball and cage prostheses have been studied in ninety-five patients.
2. Intravascular haemolysis has been found to be common and particularly marked after an aortic valve replacement.
3. A simple and reliable method for estimating urinary iron is described, and excessive urinary iron loss was found to be common especially in aortic valve replacements.
4. The urinary haemosiderin test has proved to be a useful screening procedure, the degree of haemosiderinuria correlating with the severity of haemolysis and also giving an indication of the amount of urinary iron lost.
5. Iron therapy is recommended where there is haemolytic anaemia with secondary iron deficiency, or prophylactically in the presence of persistent appreciable haemosiderinuria or abnormal urinary iron excretion.