In this paper, the frequency equation for phase velocity of waves propagated in a laminated medium under initial stresses is obtained. Two cases are considered, the first one a medium consisting of two elastic layers of finite thickness and the second one a medium consisting of an elastic layer of finite thickness over an elastic half space. It has been shown that under certain conditions when the wavelength becomes very small compared with the thickness of each layer, the wave approaches Rayleigh waves at the two outer surfaces with the possibility of Stonely waves at the interface. Biot's incremental deformation theory was used. The theory is derived in the context of plane strain deformation. Calculations are presented for two cases.