Although the fatal pulmonary thromboses usually follow major operations or are postpuerperal, yet purely medical thrombi do occur, and in the artery the latter are more frequently primary than embolic. The facts that the pulmonary artery functions as a vein and that the blood it conveys is more venous than that in any other vein lead it to the same thrombotic accidents to which veins elsewhere are subjected. Sepsis, anesthesia, atheromatous changes, stasis in the blood stream and low blood pressure all predispose to the formation of a thrombus, and the case reported here illustrates, we believe, such a combination of etiologic factors. REPORT OF CASE History. —A shop foreman, aged 39, entered Rockford Hospital on Oct. 20, 1929, complaining of a general sense of unrest, malaise, anorexia, palpitation, shortness of breath, easy fatigue and some aching through the chest. He had always been a hard worker. Four weeks prior