Classical plate buckling theory is used to model the buckling problem for rectangular cylinders. Solutions to the resulting equations are found directly for the case of a uniformly loaded cylinder and by approximate techniques for the nonuniformly loaded cylinder. Results from a series of experiments to determine the buckling load are presented and compared with predictions from the theory. These comparisons reveal the need to examine geometrically nonlinear buckling problems to more closely model the situation present during the compression loading of rectangular cylinders. In addition, the need to include inelastic behavior for cylinders of low aspect ratio is also revealed.