It is important to distinguish between the so-called Naegeli type of monocytic leukemia (which many regard as a variant of myelogenous leukemia, with predominance of monocytes) and the true Schilling type (leukemic reticulo-endotheliosis), in which the cells are derived from the reticular cell. A primary autochthonous cutaneous origin for either type of monocytic leukemia may be encountered, a fact which we believe is not generally recognized by internists and pathologists or even by many dermatologists. One of us (H. M.)1has previously emphasized the possible autochthonous cutaneous origin of any of the lymphoblastomas, including even myelogenous leukemia.2It is not pertinent in this paper to discuss the various hemocytologic views regarding the monovalent, dualistic and trivalent origin of leukocytes.3There is an increasing tendency in the recent literature to recognize two types of monocytic leukemia as well as the lymphatic and myelogenous types of leukemia. If one