The behavior of thin-web girders in shear, when loaded in excess of the buckling value, is studied. The equations and simplified design charts presented take into account the effect of flexural rigidity of the flanges on the strength of the web, stiffeners, and fasteners. The study is directed primarily to aluminum webs, although in theory the concepts should be applicable to webs of other materials. In the development of the ultimate strength equation, it is assumed that the stress distribution in the web is the sum of a component of pure shear equal to the shear buckling value plus two components of tension stresses, one oriented at an angle of 45°, the other oriented at an angle calculated as though the flanges were completely flexible. The relative magnitude of the two tension components depends on flange flexibility. Ultimate failure is assumed to occur when the combined stress state causes yielding of the web. The study also considers the effect of web buckles on the appearance of the girder. The calculated results are compared with experimental data for thin-web aluminum girders.