Since the demonstration of a rather high degree of proteolytic enzyme activity in the granular polymorphonuclear leukocytes, the presence of such leukoprotease in these and other cells of the blood has been studied in various conditions,1as, for example, the presence of ferments in the abnormal granular and nongranular cells present in the blood in leukemia. No studies have been reported since the development of modern microchemical methods. In this paper the results of the study of proteolytic ferment by a method applicable to small amounts of blood are described. One point of interest in the proteolytic enzyme in the abnormal cells of leukemic blood concerns the possible relation of these cells to normal lymphocytes or to the myeloblasts of the bone marrow. Small amounts of proteolytic enzymes have been described in almost all cells, and normal lymphocytes possess little more than other types of cells, while the granular