That material properties depend on the rate of loading has long been known. The purpose of this experiment was to study the mechanical response of bone and muscle tissue to impacts of varying velocity. An air gun-type testing machine was developed, capable of performing constant velocity compression tests with strain rates up to 4,ooo/sec. Adjustable stops are provided that allow predetermined strains to be applied to miniature specimens. High-frequency response instrumentation utilizing a piezoelectric load cell and a capacitance displacement transducer was used. Load and displacement histories of various materials including bone, muscle tissue, aluminum, and nylon were measured over a wide range of strain rates. Results are presented in the form of stress-strain diagrams at selected strain rates. A critical velocity was noted for bone in the neighborhood corresponding to a strain rate of ~/sec. A stress, strain, strain-rate surface representation of the data is suggested and similarities between the dynamic response of bone, nylon, and aluminum noted. The variation of the ultimate strength of bone with strain rate was found to be satisfactorily represented by an exponential.