Buckling of rectangular orthotropic plates subjected to non-uniform compressive loads is considered in this study. This involves a two step procedure - first the determination of the in-plane stress distribution using a rigorous superposition approach and then the analysis for stability using Galerkin's method. It is shown that the net critical load varies significantly with changes in the edge load distribution and such variations can be much more serious here than for isotropic plates because of slower St Venant decay. Further, the effects of various relevant parameters are examined with respect to partially loaded plates, plates with different load distributions on opposite edges, moderately thick plates and plates with simply supported/clamped edge conditions. © 2006 Elsevier Ltd. All rights reserved.