The transmission of X-rays through the glass envelopes of certain types of television tubes, or through the glass covering X-ray fluoroscopic screens, is influenced by the amount and type of high atomic number elements in the glass. Interest in this aspect of the subject was stimulated by recent findings that color television receivers have been shown to emit X-radiation. These emissions have been found to originate from picture tubes, shunt regulator tubes, and high voltage rectifier tubes. When conducting inspections of equipment where transmission of X-radiation is in question, it is useful for the inspector to know the composition of the glass so that its ability to absorb X-rays may be estimated. Lead is the element most commonly used in glass for its radiation attenuation. A rapid, semi-quantitative method for the detection and estimation of lead in glass, suitable for use in the field, has been developed. It is based on the action of a mixture of hydrofluoric acid and sodium iodide on lead contained in glass and ceramics. Important features of this test are that the reaction can be evaluated in a matter of minutes in the field without causing visible damage to the specimen, and the elimination of the conventional chemical analysis that is generally performed in the laboratory. It will show at once whether lead is present in appreciable amounts or is essentially absent.