It is intended in this paper to summarize the status of the newer agents which are available for the treatment of leukemia. Exhaustive coverage of this subject is obviously impossible in a brief review. In discussing therapy it is best to consider acute leukemia and the chronic leukemias as two separate groups, since there are certain major differences in approach. The agents available for the treatment of acute leukemia may be divided into two large classes. First, the steroid hormones, of which cortisone, hydrocortisone, corticotropin (ACTH) and prednisone are examples. In this group, it appears that prednisone and prednisolone have certain advantages over cortisone, since they produce less of the undesirable side-effects on electrolyte balance for the same degree of therapeutic effect. The original observations of the value of corticotropin in leukemia were made by Pearson and co-workers1 and Farber and co-workers.* The steroids act rapidly and are therefore of