In our experience, in half of the cases of primary hemolytic anemia in which there is no family history of anemia, jaundice or splenomegaly, examination of the blood disclosed microspherocytic erythrocytes and increased fragility of erythrocytes. The results of splenectomy in these cases are better than in those in which microspherocytosis is absent. True macrocytosis was observed in only one instance. Females predominated in both groups of cases. Agglutinins and hemolysins have not appeared to play any significant role in the production of the hemolytic syndrome in our cases. We do not feel justified in expressing an opinion as to whether the microspherocytosis indicates a familial or congenital blood disorder. From a practical standpoint, it makes no great difference since splenectomy should be considered seriously in any case of chronic primary hemolytic anemia. It may be of value in some cases of secondary or symptomatic hemolytic anemia.