A case of promyelocytic leukemia is presented. It was characterized by 1) a clinical picture of acute leukemia, 2) predominance of promyelocytes in the bone marrow smear, 3) predominance of promyelocytes (as the abnormal leukocyte) in the peripheral blood, 4) a rapidly fatal course and 5) necropsy findings of acute myelogenous leukemia. Unfortunately, the patient died before plasma fibrinogen and other clotting factors could be determined. Promyelocytic leukemia has only recently been considered as a distinct clinical entity. Fibrinogenopenia seems to be a constant finding. The use of 6-mercaptopurine plus corticosteroids apparently produced remissions in two of the 24 patients reported in the last 4 years.