In this review we propose to compare the results obtained from roentgen therapy in a group of 125 cases of proved primary bronchiogenic carcinoma with another group of 125 proved cases in which neither roentgen therapy nor any other form of therapy was employed. Considered here, a proved case will be regarded as one in which tissue from the tumor on microscopic examination has shown the presence of carcinoma. In all cases in our study there was microscopic confirmation of the clinical diagnosis. This point is important, because we know from experience that to make a differential diagnosis between primary carcinoma of the bronchus and other types of pulmonary lesions is often difficult. Although roentgenologic examination of the thorax is of the utmost importance in the diagnosis of this condition, it is well known that considerable inaccuracy exists in precise differentiation between primary carcinoma and other lesions by this method.