The theoretical and experimental effective elastic constants and stress multipliers which have been proposed for materials perforated in a square pattern of holes are critically examined.The theoretical values obtained by Hulbert and the corrected values of Bailey and Hicks are found to be accurate, both from theoretical considerations and by virtue of comparisons with extensive experimental data obtained by Bailey and Hicks; Nuno, Fujie, and Ohkuma; Duncan and Upfold; and Saito, Leven, and Stepanek.An improved axisymmetric approximation is given for the corresponding simply supported aeolotropic circular plate subjected to uniform pressure.This approximation satisfies the condition that the average radial moment at the periphery is zero, whereas the approximation proposed by Okubo does not.This improved approximation, and the appropriate effective elastic constants and stress multipliers were then used to analyze the perforated plate tests sponsored by PVRC at SwRI.Satisfactory agreement between the theoretical and experimental results is found for both stresses and deflections.