That an abscess of the lung may perforate into the pleura has been known for a long time, but that this is a fairly frequent occurrence and that such an event augurs rather well for the patient, as far as cure of the abscess is concerned, is not so well known. I therefore feel justified in presenting this subject on the basis of ten patients who were observed during the last few years. The relation of empyema to intrapulmonary suppurative lesions is naturally an interesting one and has received considerable attention during and since the Great War. It has been reasoned by analogy with inflammatory conditions in the peritoneum that the inflammation of the pleura, in cases of empyema, is not primary but is secondary to an inflammation of the tissues underlying it. Several authors have gone so far as to state that all, or nearly all. empyema cases are