Recent comparative x-ray studies demonstrate: (1) Photofluorography is a relatively efficient tool for tuberculosis case finding. (2) All photofluorograms should be interpreted independently by two competent interpreters. (3) The activity of a lesion cannot be determined from a single roentgenogram. There is a variation in film interpretation between different observers, similar to that noted in many other fields which have been subjected to valid test. This variation is now the source of extensive investigations, out of which should come considerable progress in all branches of medicine.