The concept of a macrokinetic distribution (MKD) is used to develop a theory of nonequilibrium carrier transport in multivalley semiconductors. The MKD is a momentum‐dependent function with macroscopic space‐time scales, whose equation of evolution is macroscopically equivalent to the semiclassical Boltzmann transport equation for the phase‐space distribution. A MKD is obtained for each valley and used to close the set of coupled moment equations that describe carrier transport in each valley. The resulting set of equations constitutes the model. A two‐valley model is developed to illustrate the theoretical procedure. Results are obtained for the response of electrons to a rapidly varying (in time) electric field. These results are compared to those obtained using Monte Carlo (MC) methods and also an equivalent single‐valley model. Excellent agreement is obtained between the macrokinetic model and the MC results. The single‐valley model is shown to be inadequate in situations where intervalley carrier transfer is significant.