In the past two years a great deal of effort of the Tuberculosis Control Section, U. S. Public Health Service, has been given to mass x-ray surveys for the prime purpose of tuberculosis case finding.1 Both the 35 mm. and the 4 by 5 inch photofluorograph have been used as a screen to separate persons with chest abnormalities from those with essentially normal chests. Most of the surveys were accomplished with 35 mm. equipment. From April 1942 to March 1944, 685,817 chest x-ray films were taken and 1.4 per cent were found to give x-ray evidence of reinfection tuberculosis. Over 60 per cent of the lesions were in the minimal stage.
In the course of looking for tuberculosis a great many chest conditions other than tuberculosis were encountered. The discovery of nontuberculous pathologic changes forms a valuable by-product of mass x-ray surveys.
The preponderance of individuals found with abnormalities