Non-linear differential equations have been developed for the calculation of the deflections and buckling loads of Sandwich plates subjected to transverse loads and edgewise shears and compressions.The Sandwich plate consists of two thin metal face sheets bonded to a light slab-the core. The core is taken to have zero moduli as deformations in its own plane. This appears to give an adequate representation of behavior of many core materials.Some previous theories are shown to be special cases of this more general theory. The essence of non-linearity are shown through the dicussian of core properties and action of interface-and-core forces. The restriction of some special forms of displacements of practical interest has been studied and the existence of nonlinear element in the bending problem is clarified. The relative merit of using large bending deflection theory instead of the small bending deflection theory in the faces is given.