When creating high-voltage electrotechnical devices, the selection of the impregnating liquid dielectric is especially important. Along with the usual requirements such as high electric strength, low dielectric loss, resistance to the effect of partial discharges, resistance to gas, liquid dielectrics should possess a number of special properties; their compatibility with structural materials is the principal one. Liquid dielectric compatibility with structural materials is considered to mean not only the fact that the used structural materials shouldn't cause substantial reduction of the electrophysical parameters of a liquid dielectric but the Abstract -The influence of structural materials on the principal electrophysical characteristics (relative permittivity, loss tangent, volume electric resistivity, and electric strength) of polymethylsiloxane liquid PMS-10 is considered in the paper.