It has been estimated that in 1970, 129 million people in this country were exposed to 210 million medical and dental X-ray examinations. According to the U.S. Bureau of Radiological Health, about 30% of the X-ray exposure does not contribute any useful information to the radiologist. There is no doubt in the mind of anyone that the advantages gained from X-ray examinations far exceed any possible late biological effects resulting from this exposure. All radiologists employ equipment and techniques designed to decrease X-ray exposure as much as possible while providing adequate diagnostic information. Still, there is increasing concern on the part of radiation scientists that medical and dental X-ray examinations are a significant public health hazard because of their increased frequency of application.