Because of the high incidence of tuberculosis among persons who have been exposed to massive infection from others, x-ray examinations of such contacts have been a routine practice in the Chest Clinic of the University of Chicago since 1929. The convincing experience that early tuberculosis is most successfully found among those who, because of the absence of symptoms, are unsuspected led in 1932 to the initiation of a case finding program among students, faculty and hospital employees. The results were in keeping with those reported from similar institutions and gratifying enough to continue the examinations as a university and hospital routine. In 1934 the practice was extended to the expectant mothers seen in the clinic of the Chicago Lying-in Hospital because of the many unpleasant experiences with previously unrecognized tuberculosis among that group of patients and because they are an easily accessible group of healthy although physiologically strained persons. To