The theory of stimulated Raman scattering using the coupled-wave approach is extended to include the case of polar media, with and without inversion center. Mixed effects of parametric down-conversion and Raman emission may occur. The threshold of the stimulated Raman effect in these media should not be much higher than that in a nonpolar system. The mixed effects of parametric down-conversion and stimulated Raman emission are also considered in purely electronic systems. They may be observable if the Raman transitions have a narrow linewidth.