The authors previously investigated the effects of both shear and normal strains in the viscoelastic core layer on modal properties of sandwich plates under hinged boundary conditions. For such boundary conditions, analytic formulation of characteristic equations was possible. Agreeing that most real boundary conditions must lie somewhere between hinged and clamped, it is naturally worthwhile to solve for the clamped boundary conditions, for which, however, analytic formulation of the characteristic equations is not possible. In this study, hence, the finite difference method is utilized as a tool for numerical analysis. The effects of neglecting the extensional or compressional strain in the core material for the clamped boundary conditions are studied and compared with the case of simply supported boundary conditions. (C) 1999 Academic Press.