A special theory of rectilinear flow of a polarizable liquid is developed by introducing a polarization parameter into the stress‐rate‐of‐strain relationship of the liquid. The viscosity of the liquid is thus dependent on its state of polarization, and this in turn is determined by the shear rate, the strength and direction of any applied electromagnetic field, and the proximity to an interface. Formulas for the effects of these influences on the apparent viscosity are developed for the case of large shear rates. Comparison of these formulas with three published sets of viscometric data—Couette flow with an electric field, Poiseuille flow with a magnetic field, and Poiseuille flow with interfacial effects—on nematic liquid crystals show excellent agreement of the theory with the data.