Stress-strain relations have been obtained in compression at medium strain rates for selected plastic materials suitable for shock mitigation. Data were acquired at room temperature, and at 200F and 350F for those materials capable of withstanding the elevated temperatures. Rates of strain between 0. 004 in/in/sec and 60 in/in/sec were obtained using a conventional high-speed testing machine. Most of the materials investigated exhibited strain rate sensitivity over the range tested.