The unusual high and low-temperature properties of silicone rubber have made it a desirable material for vibration isolators designed for service at temperature extremes. In general, silicone cannot be substituted directly for such elastomers as natural rubber and neoprene in established designs. This lack of interchangeability results principally from the lower tensile strength and the unusual load-deflection characteristics of the material. A program to investigate the dynamic properties of silicone rubber was undertaken to provide the design engineer with information which would allow the material to be utilized properly. This paper deals with the viscoelastic properties of silicone rubber under various conditions of strain, frequency, and temperature. Where possible, comparisons are made with natural rubber.