Summary: Difficulties have been encountered in applying stability constraints to statically indeterminate structures other than the determinate. The proposed approach is an extension of the conventional optimum designs by considering that the subsequent change of structural internal forces is no more negligible from stability constraints than for statically indeterminate structures, although they may need considerably longer computer run times. The optimization technique employed is based on the multipliers method. The incipient buckling of the structure is determined by a linear eigenvalues solution. The method is programmed for thin- walled trusses and frames. A number of sample structures are given and the accuracy for indeterminate approach is shown to give a better optimum solution.