The difficulty in the evaluation and interpretation of shadows seen in roentgenograms of the chests of a group of children enrolled in a clinic for tuberculous children and for those in close contact with tuberculous persons has prompted this study. In the region in which New Haven is located most children are subject to more or less frequent infections of the upper respiratory tract. Such children, as well as those with frank pulmonary infections, often show thoracic roentgenographic markings of one type or another which are difficult or impossible to differentiate from shadows caused by tuberculous lesions. In the roentgenograms of the chests of children reacting negatively to tuberculin, shadows are often seen which are similar in location and appearance to those observed in the roentgenograms of children reacting positively; the interpretation of the shadows is often influenced by a knowledge of the reaction of the patient to tuberculin. In order to discover any differential factors in comparable roentgenographic shadows caused by pathologic lesions of varied etiology, roentgenograms should be studied in the light of the case as a whole: first, in careful conjunction with the clinical history and laboratory data, and second, in relation to the postmortem observations. Anatomic control is of great importance From the