A new approach to the problem of minimum‐weight design of stiffened compression panels is presented. It is predominantly based on the plate instability mode in which the sheet and stiffeners, having been stressed to the same degree, simultaneously buckle over a long wavelength with the length of a buckle equal to the pin‐ended length of a panel. Charts to determine the buckling stresses of the modes required for the minimum‐weight design are given. Formulae and charts are presented to compute the effective moment of inertia of a stiffener, a most important quantity, over a wide range of panel proportions, for Z‐section and integrally machined unflanged stiffeners. The principles of minimum‐weight design are discussed and illustrated by the lightest Z‐stiffener panels selected from extensive test data. Comparison of the theoretical stresses of the optimum panels and many other panels of different proportions with those obtained by tests shows good agreement. The principle of dimensional similarity, which is implicit in the buckling mode referred to above, eliminates the effects of size. Results obtained either from theory or tests can therefore be applied to different size panels of like proportions.