SummaryNew immunological methods show anti-red cell antibodies in most cases of acquired hemolytic anemia.The case of a 66 years old woman presenting this disease is described. Her blood contains warm agglutinins and her Coombs test is positive (direct).After administration of A.C.T.H. during 15 days no improvement was noted. Cortisone induced a temporary remission but cure was only obtained by splenectomy (follow-up of 6 months).Abnormal antibody titer shows little change despite the remarkable improvement which followed cortisone therapy and splenectomy.The origin and mode of action of auto-antibodies remain uncertain. Equally mysterious are the modes of action of splenectomy and hormone therapy. Nevertheless, cortisone or A.C.T.H. constitute at present the best treatment in acquired hemolytic anemia. When this therapy fails, the patient should be submitted to splenectomy. The results of this operation are as unpredictable as those of hormone therapy, but failure of one type of treatment does not imply, ineffectiveness of the other.