A 15-year-old boy, admitted with a two months’ history of chest pain, cough, pallor, and progressive loss of energy, was found to have a right pleural effusion and pancytopenia; a diagnosis of acute myelogenous leukemia was made on bone marrow and peripheral blood examination. Blood transfusions, chemotherapy, and aspiration of pleural fluid effected a temporary clinical improvement, but the hematologic status continued to deteriorate. The temperature was elevated to 101 F. Cultures of blood, urine, and pleural effusion were negative. Twelve hours before the patient’s death the temperature rose to 103 F., and he had severe chest pains. Later, he became delirious, and had shallow grunting respirations and tachycardia. He died on the eleventh hospital day. At autopsy, the leukemic cells, identified as promyelocytes, were found infiltrating many organs. There were coagulase-positive staphylococcal septicemia, pneumonia, and pleuritis; hemorrhages into several tissues; and disseminated intracapillary or sinusoidal thrombosis in the lungs, liver, adrenal glands, and kidneys. Fibrin was a prominent component of these thrombi. The possible mechanisms of consumptive coagulopathy in acute promyelocytic leukemia are discussed.