A new scheme of backward Raman scattering, in which coupling between the forward and backward Stokes processes is caused by injecting an additional backward pump ®eld, is demonstrated both experimentally and theoretically. Four wave mixing among the pump and Stokes ®elds leads to gain enhancement of backward Raman scattering. A factor of gain enhancement of 2 was obtained with injection of a 0.4 mJ seed Stokes and a 5 mJ backward pump wave.