Severe, traumatic, cardiac, hemolytic anemia developed in a patient nine years after mitral valve replacement with a Starr-Edwards model 6120 prosthesis. Cardiac catheterization failed to demonstrate a perivalvular leak or prosthetic malfunction. Transfusion on two occasions resulted in accelerated hemolysis and failed to maintain an appreciable elevation of the hemoglobin level. At operation, a perivalvular leak was found. Replacement of the valve led to complete resolution of the hemolytic problem. The case demonstrates that cardiac hemolysis may be a good indicator of valve dysfunction.