A consideration of the possibilities and limitations of roentgen examination in the diagnosis of chest conditions is, in effect, an effort to estimate the value of the roentgen method. Such a consideration must begin with a division of roentgen findings into those which lead to the detection of an abnormal process and those which lead to the identification of the nature of the lesion. While in some situations the discovery of an abnormality in the roentgenogram may carry with it an almost certain determination of its etiology, more commonly identification must rest on more elaborate studies with the use of numerous other diagnostic methods. It is in the discovery of lesions that the roentgen examination has its greatest usefulness and likewise its greatest reliability. With the rapid advancement in the technic of roentgenography, the utilization of mass surveys, and the widespread recognition of the necessity for roentgen study of all