Leaky Lamb waves have been used extensively for ultrasonic non-destructive evaluation of elastic properties: the reader is referred to papers by Dayal and Kinra [1,2], Chimenti and Martin [3], Mal et al.[4], and Chimenti and Nayfeh [5]. The principal disadvantage of this method is the high attenuation of the waves in the immersed solid plate due to continuous radiation to the surrounding fluid. As a result, their amplitudes become immeasurably small after a short distance of travel as observed by Dayal and Kinra. This provided the motivation for the present work: a study of the propagation of harmonic waves in a solid plate loaded by a fluid layer of a finite thickness. In a previous work by the authors [6], the dispersion equation for an isotropic solid/fluid bilayer was obtained. It was seen that a thin layer of fluid coupled the symmetric (5) and antisymmetric (A) modes in the solid layer and that along a branch a quasi-symmetric mode changed character to a quasi-antisymmetric mode near a region where previously the S and the A branches crossed but were uncoupled. In the present work the dispersion equation for an orthotropic solid/fluid bilayer is derived. Mode shapes are studied for a graphite-epoxy/water bilayer for the case of equal thickness of the fluid and solid layers. In this case, coupling between fluid and solid modes is observed.