In this report, attention will be called particularly to primary cancer of the lungs. However, for the purpose of discussing certain references to probable determining etiologic factors, attention will also be called to the cases of secondary carcinoma which occurred in our experience during the same time that the primary cases occurred. Carcinoma of the lungs in the most recent studies shows a much higher incidence than was formerly thought. It has come to be recognized as occurring comparatively frequently; so much so that in the consideration of diseases of the chest, especially of the chronic form, one should always hold in mind the possibility of primary carcinoma of the lungs. Various causes have been suggested to explain this remarkable increase. As yet there is no agreement among clinicians and laboratory men. The accumulated evidence of many case reports may help to clarify the matter, and this is our reason