The dynamic stress‐strain‐time response of a clay in compression is studied using a high‐speed explosive pulse type of apparatus. The rise times of the applied stress pulses are the order of magnitude of 0.2 msec and the entire test durations are approximately 3.0 msec. Compressive loading is obtained with a piston using the high pressure developed by firing a Springfield 30–06 cartridge into a combustion chamber. Measurements include forces at the top and bottom of the test specimen, deformation of the specimen, and acceleration as well as velocity of the upper platen. Dynamic stress‐strain response exhibits an under‐linear type of nonlinearity for a wide range of consistencies (moisture contents) generally encountered in field applications. Effects of moisture content are conveniently handled in terms of a nondimensional dynamic stress‐strength parameter using the static ultimate unconfined compressive strength as a consistency index. The nonlinear effects are represented in terms of a two‐constant hyperbolic stress‐strain relation. The two hyperbolic constants are measures of the initial tangent modulus and the ultimate strength of the clay. These constants are easily obtained as the intercept and slope of the straight line approximation of the experimental data when presented in transformed hyperbolic coordinates. Because of the multiphase nature of clay, the results may be of value in studying the response characteristics of other composite materials.