In this work a theory of the degenerate four-photon parametric scattering (FPS) is developed in a liquid suspension of transparent microspheres (heterogeneous medium), the nonlinearity of which is caused by the change in the microsphere concentration under the action of gradient forces in the electromagnetic field of interacting waves. It is shown that the water suspension of latex spheres with diameter d = 0.234 μm and concentrationN0 = 6.5·10 cm, in effect of the FPS process, corresponds to a cubic nonlinear medium with the optical Kerr coefficient n2 that is larger by a factor of 10 than in the case of CS2.