This report presents the results of a study of the local buckling strength of steel columns. The effect of residual stress is given attention. The finite difference method was employed throughout the analysis and proved to be a suitable method for obtaining solutions for this type of problem. Numerical results are presented for plate buckling curves for plates with idealized residual stress distributions of various magnitudes. The boundary conditions of the plates are simply supported at the loading edges, and four combinations of free, simply supported and fixed at the unloaded edges. An illustrative result is also presented for the local buckling of a column cross section. The theoretical results were correlated with experimental results of eight pilot tests of square welded columns of ASTM A7 and A514 steels. I.