Recent reports (1, 2, 3) have focused the attention of the medical profession and of the general public on the hazards of diagnostic roentgenology. At the same time, radiologists have felt the need for shorter and shorter exposures in many situations, particularly in angiocardiographic technics (4). The ideal solution of this problem would be a reduction in exposure time with a decrease in radiation exposure to the patient, without sacrifice of the diagnostic quality of the image. Recent progress in the photographic field has resulted in the development of extremely fast panchromatic emulsions. The ASA speed of these films, when properly handled, is from 320 to 2,000 per cent higher than that attainable with the usual emulsions. In view of the fact that the formation of the image on x-ray film is mainly due to the visible light fluorescence of the intensifying screen (98–99 per cent), it appeared that progress made in the photographic field should be exploited in roentgenography with intensifying screens. Such a screen should fluoresce in the region of the spectrum to which the emulsion is most sensitive (5). When intensifying screens were first introduced in 1886, the emulsions available were of the so-called “ordinary” or color-blind type. Their peak sensitivity was at about 4,300 Å. The intensifying screens, therefore, were fabricated to have their peak emission at the same wave length. Today, as we have indicated, the fastest films are panchromatic. Thus, it seemed logical to employ a different type of screen, the peak emission of which would match the peak spectral sensitivity of the most sensitive contemporary photographic emulsions. Ordinary fluoroscopic screens appeared to be suitable for preliminary investigation of this hypothesis, not only because of the wave length of their light emission, but also because they are more efficient than conventional intensifying screens (6). Three films and three screens were selected for the present investigation. Two of the films were x-ray films: Kodak Blue Brand and Kodak Royal Blue. The third was the single emulsion Panchromatic Kodak Royal X. They were developed in “Kodak Liquid X-ray” at 68° F. The screens selected were DuPont-Patterson Par Speed, Lightning Special, and CB2. The apparatus used was a Westinghouse Fluoradex 300.3 Accuracy of the thermionic timing device was checked with a constant-speed stroboscopic wheel and an Electromec 21-inch Oscilloscope, Model 2135A. A G.E. Penetrometer, Model E8038A, was used, and the densities of the exposed films were determined with a Kodak RT Color Densitometer. All screen-film combinations were studied. The results are summarized in Table I. The significantly greater sensitivity of the CB2-Royal X combination is evident; in addition, its latitude and contrast range proved to be by far the widest obtained with any of the screen-film pairs used.