Many new phosphors for x-ray intensifying screens have been developed during the past decade. Most of these materials are more efficient in absorbing x-ray photons and in converting them to light than older more conventional phosphors. Objective criteria used to evaluate and compare different screen-film systems are described. Speed, sharpness, contrast, mottle, and the effect of each on the other are discussed. New x-ray films have been designed for usewith these phosphors. Some have extended sensitivity to match the spectral light emission of the screens, others also have improved cross-over characteristics. Theoretical foundations for combining the new screens and films for improved radiographic images are developed. (Abstractor's note: The use of an intensifying screen can significantly reduce the x-ray exposure required to make a satisfactory image on the film.) -- AATA