This paper deals with the theory of degenerate four- wave mixing (DFWM) in trantarent and absorbing media. The values of third order nonlinear susceptibilities χ(3) and nonlinear refractive index n2 in semiconductor doped glass, inorganic and organic media were given experimentally. The time response properties of the nonlinear susceptibility χ(3) was also determined. Time resolution of the experimental device is 5 ps.