Following an episode of rheumatic carditis, severe mitral incompetence developed in a 9-year-old girl. A mitral annuloplasty succeeded for a short time in ameliorating her symptoms of cardiac failure. However, mitral incompetence recurred and was accompanied by severe anemia and hemosiderinuria. Distortion of erythrocytes was evident on a peripheral blood smear. A second mitral annuloplasty resulted in resolution of the hemolytic anemia.