Certain types of neutron diffusion calculations were considerably simplified when the Serber.Wilson Method was introduced about eight years ago. This method, semi-empirical In nature and named after its co-discoverers, was first formulated for the one-velocity isotropic theory and applied to spherical geometries. Within these limits it has in general proved to be a fairly accurate method. If restricted source-free case it has, in addition, turned out to be quite manageable both analytically and numerically.