The small-deflection theory of orthotropic sandwich plates developed by \textit{C. Libove} and \textit{S. B. Batdorf} [NACA TN 1526 (1948)] is extended to highly anisotropic sandwich plates with thin faces. Buckling coefficients of a simply supported rectangular symmetrical anisotropic sandwich plate under combined longitudinal compression and bending are evaluated using the Rayleigh-Ritz method. The results show that the multi-ply-faced orthotropic sandwich plate is stronger than a single-ply- faced anisotropic one and that the maximum longitudinal buckling strength occurs in plates with lower aspect ratios when the reinforcing fibers are longitudinal and in plates of higher aspect ratios when the fibers are oriented at about 40 deg with respect to the longitudinal axis.