The Stokes parameters of scattered light are given by the matrix equation $$(s_0,s_1,s_2,s_3)=F(s_0^0,s_1^0,s_2^0,s_3^0)$$ where the 4, 4 scattering matrix $F$ is comprised of 16 scattering matrix elements. These matrix elements, which may originate in theory or experiment, provide a complete description of the scattered radiation in terms of the incident radiation.