Evans syndrome is defined as the simultaneous or sequential occurrence of Coombs' positive hemolytic anemia and immune thrombocytopenia without known underlying etiology. Ten cases of Evans syndrome were seen at our hospital over the past decade; three patients died. Two cases are described in detail and demonstrate the chronic, refractory nature of this condition. Most patients have required corticosteroid therapy and splenectomy, but further therapy (e.g., intravenous gammaglobulin, danazol, cyclophosphamide) is usually necessary because of recurrent autoimmune hemolytic anemia, thrombocytopenia, or both. There is a substantial risk for development of other autoimmune problems and hypogammaglobulinemia. A number of defects in humoral immunity have been described in Evans syndrome; different antibodies are directed against platelets and red blood cells. Cellular immunity is probably abnormal, but a distinct pattern of immunoregulatory disturbance has not been identified.