Dynamic light scattering studies of polystyrene (PS) in tetrahydrofuran (THF) in 1,4-dioxane (DO) and in THF/DO mixed solvent, subject to an external de field, have been carried out. In THF the rate constant for the decay of the intensity autocorrelation function (IACF) is found to increase with increasing the external applied electric field; in DO, the electric field is found to have only a negligible effect on the IACF; in the mixed solvent it exhibits an intermediate effect, depending on the THF content. A hydrodynamic theory is proposed to account for the observed electric field induced effect in THF.