Force on dielectric fluids in the presence of a nonuniform electric field is shown to reduce their specific weights. An appropriately chosen field gradient makes the specific weights of superposed fluids equal and prevents Rayleigh–Taylor instability. We derive the dispersion relation for perturbation at the interface of superposed dielectric fluids, within limits of linear theory, successively for ideal, Newtonian, and those with stratified viscosity. A dimensionless dielectric number is shown to determine the stability of the arrangement.