Cold agglutinins are serum antibodies activated at low temperature to produce red blood cell agglutination and hemolysis. Hypothermic cardiopulmonary bypass has potential danger to patient with positive cold agglutinin titer. We report a successful anesthesia for mitral valve replacement surgery in a patient who has high cold agglutinin titer. To avoid problem, the cold agglutinin titer was reduced by plasmapheresis and hypothermia was maintained above the critical temperature. There was no severe complication except mild hemoglobinuria.