Glasses in the system Pb0–Al2O3‐B2O3‐SiO2are chemically stable over a wide composition range and have very desirable electrical characteristics such as high electrical resistivities and activation energies for conduction. Variations in these electrical properties were studied as a function of composition changes within the system, the object being to identify the role of the constituent oxides in achieving the highest activation energy and resistivity values consistent with moderate preparation temperatures. Measurements were made in the temperature range 25° to 400°C on carefully prepared glass disks in which the individual oxide components or different oxide ratios such as PbO/SiO2, Al2O3/SiO2, and BsO3/SiO1were systematically varied. The activation energy and resistivity values obtained ranged from 1.2 to 1.6 ev and 10° to 1014ohm‐cm, with dielectric constants ranging from 9 to 19 and densities from 4.30 to 4.50 g/cmY. Indications were that, for the composition range studied, the behavior manifested was basically that of the binary PbO‐SO2glass with additions of Al2O3or B2O3, even in small concentrations, sharply increasing the activation energy for conduction while lowering