The greatest danger of carcinogenesis and of genetic damage through diagnostic radiologic procedures is in children, whose smaller bodies are more vulnerable and who have a longer life span in which this damage can be realized. Film badges placed on the gonad area during radiologic studies indicated widely varying degrees of gonad irradiation from similar procedures. These results emphasize the importance of technique in protecting children from unnecessary exposure. Such exposure can be reduced by greater beam filtration, use of higher tube potentials, careful beam collimation and centering, closer coning and shielding of the gonads. A new film tested reduced exposure time by 50 per cent. Further reduction was obtained by high-speed screens.A most important measure is avoidance of unnecessary, repetitious and undiagnostic studies. Fluoroscopy should be avoided if possible. If not, the operator must dark-adapt his eyes, use the smallest possible current, the narrowest beam, and the shortest exposure time. Image intensification promotes these aims. Modern equipment, properly shielded, assures against unsuspected exposure.