The electrohydrodynamic stability of a plane layer of nonpolar liquid is analyzed under certain basic assumptions. The liquid is supposed to be perfectly insulating, the space charge resulting from a unipolar injection of charge. The injection is considered to be nonautonomous, that is, following a field dependent law. The regions of linear stability under stationary conditions have been computed both in terms of nondimensional parameters and directly measurable variables, such as the applied voltage and the gap spacing between the electrodes. The results have shown that the onset of instability is strongly dependent on an injection strength parameter and can be approximated by the linear criterion corresponding to autonomous injection, provided that the injected charge is given by the injection law. Experiments have also been performed to determine the instability threshold under transient conditions. An interpretation of these experiments has been done by generalizing an approximated theoretical study for autonomous injection to the case of a nonautonomous injection. ©1995 American Institute of Physics.