A theory of intensity scattering from a multi-layered random medium with irregular boundaries is developed using the radiative transfer formulation. Explicit forms for the zeroth and first-order solutions are given. Special cases are shown and compared with previous results. The similarities and differences between the results of this and previous studies are pointed out. In particular, terms omitted in previous studies are indicated and previous scalar or partially scalar formulations are generalized to permit a complete polarization treatment.