The relative frequency and increasing tendency toward the occurrence of primary cancer of the lung has prompted me to make the following correlation. The clinical data was obtained through the cooperation of the various medical and roentgenologic departments. In reviewing the autopsy records from October, 1929, to November, 1930, 50 cases of primary cancer of the lung were found. The total number of autopsies made during this period was 3,064, the relative frequency of cancer of the lung being, therefore, 1.5 per cent. Deducting the number of autopsies made on persons 30 years of age or under left 2,209. The incidence of cancer of the lung in this group over 30 years was therefore 2.26 per cent. I shall first consider the clinical aspect of this disease. In an endeavor to find some of the possible etiologic factors, the following observations were made: Of the group studied, 78 per cent