This report reviews the medical diagnostic process involved in determining the pathological condition of a patient made on the basis of available roentgenological information. Several years ago, a program of work on the physics of diagnostic roentgenology was established at the Johns Hopkins University. The general purpose of this program was threefold: (1) to carry out a fundamental study of the parameters of an imaging system that affect image quality; (2) to devise methods to measure these parameters; and (3) to make available to the field of radiology the results of these measurements on apparatus currently available in the United States. The manner in which the measurements were analyzed and a summary of the characteristics of radiographic films and screens currenlty available in the United States are included. Detailed data from the measurements are not included because of their bulk; these data will be published as a separate report in the Environmental Health Series. A set of tables and curves are presented in the appendix of this report to indicate the format in which the data will be published. (Author)