A case of congenital hypoplastic anemia is reported in which a course of ACTH was followed by evidence of remission in the peripheral blood and marrow. The remission had been maintained for 10 months by administration of cortisone. The effectiveness of an interrupted regimen of administration of cortisone in maintaining remission and yet avoiding clinical signs of hypercorticism is described. An abnormality of tryptophan metabolism, as evidenced by the finding of anthranilic acid in the urine was noted. The anthranilic aciduria persisted during cortisone therapy despite a beneficial effect on production of reticulocytes and hemoglobin. Concentration of tryptophan in the blood and urinary excretion of 5-hydroxyindole acetic acid were normal.