The necessity for a "total x-ray survey" in certain areas of high mortality in Chicago has long been realized. By total survey is meant survey, in the district selected, of every man, woman and child, reaching toward an ideal though probably unobtainable objective of 100 per cent. The reasons for such an effort were compellent. In Chicago the tuberculosis problem, largely enclosed in the Negro (281.7 per hundred thousand mortality against 34.0 per hundred thousand mortality in the white population) is, to a certain extent, geographically circumscribed. In 1939 six predominantly Negro census districts, with 17.5 per cent of the population, accounted for 47.8 per cent of the tuberculosis deaths. An x-ray project of the magnitude indicated was far beyond our means in terms of the standard film and the project, necessarily, was held in abeyance. Finally. with the advent of x-ray photography, practically initiated by Manoel De Abreu of