A 72-year-old woman, who had been treated for autoimmune hemolytic anemia with prednisolone and azathioprine since 2002, was found to have mild aortic stenosis in 1994. In December 2003, she suffered congestive heart failure, and was on temporary mechanical ventilation. In February 2004, the maximum pressure gradient between left ventricle and aorta increased to 115.8mmHg on echocardiographic examination. On April 6, aortic valve replacement was carried out with a 19mm bioprosthesis (Carpentier-Edwards PERIMOUNT^®, Edwards Lifesciences, Irvine, California). Preoperative prednisolone administration was continued until the day of the operation. Four packs of washed red blood cells were transfused intraoperatively and four packs of red blood cells were transfused postoperatively. Before transfusion, haptoglobin and water-soluble prednisolone were administrated to prevent hemolysis. Oral prednisolone and azathioprine were reestablished on the third postoperative day. Her postoperative course was uneventful and she did not suffer either infection or hemolysis. She was discharged on the 30th postoperative day.