The constant increase in the number of cases of diaphragmatic hernia that are being recognized is due chiefly to the marked advance that has been made in the methods of roentgenologic diagnosis. Moreover, the clinician is considering the possible presence of a hernia in the differential diagnosis of obscure and atypical complaints referable to the upper part of the abdomen and the lower part of the thorax, and he is having special roentgenologic studies made of these patients. The more frequent recognition of diaphragmatic hernias in recent years is exemplified by reviewing the cases seen at the Mayo Clinic between 1900 and 1933. From 1900 to 1925, 30 cases were recognized clinically and 19 patients were operated on; from 1925 to 1933, 147 cases were recognized and 60 patients were operated on. This shows that approximately five times as many cases were recognized in the last eight years as in