The method of plastic upper bound analysis is developed to solve problems involving three-dimensional loading and deformation of anisotropic materials. Experiments are conducted to evaluate the applicability of the analytical results. This method is also used to predict the effect of material strength properties on the lateral deviation force on a wedge during indentation of anisotropic plastic materials. The results show that the method does provide a fairly good upper bound for the indentation force and it also gives a reasonable explanation of the experimentally observed lateral deviation force.