The problem considered is the elastic large deflection analysis of thin, rectangular, specially orthotropic plates with two axes of symmetry. Coan’s method [J. M. Coan, J. Appl. Mech. 18, 143-151 (1951; Zbl 0044.395)] for allowing the prescription, for isotropic plates, of the in- plane tensile or compressive loading along two opposite edges, is adapted to deal with orthotropic plates. This analysis has been incorporated into an existing computer program (ELDAROP), and the results agree well with previous work on isotropic plates. Results are given for the post- buckling of square orthotropic plates under uniaxial in-plane compression. These confirm that if the unloaded edges are maintained straight, the post-buckled stiffness increases, and this effect decreases as the modular ratio increases.