A 38-year-old man was admitted to our hospital because of exertional dyspnea in February, 1990. The patient had already been diagnosed as having autoimmune hemolytic anemia (AIHA) in February, 1982 and treated with prednisolone (PSL) until January, 1988. The laboratory examination confirmed the relapse of AIHA (IgG-warm type) and additionally disclosed the marked decrease of CD4+CD45RA+/CD4+ ratio in peripheral blood lymphocytes. Thereupon, the patient was treated again with PSL and entered the remission in one month. Simultaneously, CD4+CD45RA+/CD4+ ratio also increased to the normal level. Afterwards, the remission had been maintained for about six months with a small dose of PSL. However, in September, 1990, the hemolysis relapsed with marked thrombocytopenia and decreased CD4+CD45RA+ ratio. Then the diagnosis was corrected to Evans' syndrome because PAIgG was highly elevated together with positive Coombs' test. Although danazol and azathioprine were administered in addition to PSL, the disease remained in active phase. Thus, splenectomy was carried out in March, 1992. Consequently, the patient entered the remission that has been maintained over six months. CD4+CD45RA+/CD4+ ratio was also normalized. These results suggest that CD4+CD45RA+ cells may play an important role in the pathogenesis of AIHA or Evans' syndrome.