The procedure used in calculating gonadal X-ray exposure resulting from diagnostic radiographic examinations conducted in private physicians' offices in New York City is presented. The data collected in this study include technical and patient information relating to 47,000 radiographic exposures gathered in a sample consisting of 679 offices, each supplying data on all examinations and patients for a one month period. Since direct measurement was precluded by the nature of the sample, a unique approach was devised to calculate the gonadal dose for each exposure for the purpose of ultimately arriving at the genetically significant dose to the population.The method is predicated on: (1) a one point calibration of each radiographic unit which includes output and HVT determination; (2) a procedure which can predict output and HVT at any kVp for that unit to within 4 per cent; (3) an accurately determined set of measured gonadal doses in a realistic human phantom; and (4) a procedure for realistically modifying these doses for the anthropometric characteristics of any patient and the technical variables associated with specific examinations.