The production of light structural steel shapes from sheet steel, by cold forming and spot welding, necessitates the development of special design methods adapted to the peculiarities of such members. One of the questions of most practical importance is that of the strength and behavior of thin, wide flanges in compression. This paper reports the results of, and conclusions drawn from, an extensive experimental investigation of this problem. The strength, general behavior, and deformation of two types of structural elements are investigated-(A) members with compression flanges both of whose longitudinal edges are stiffened adequately (such as top flanges of inverted U-beams); and (B) members with compression flanges only one of whose longitudinal edges is stiffened (such as either half of a flange of an !-beam). Results of these tests are evaluated in terms of formulas and charts by which the strength, deformation, and general behavior of such members can be predicted under load conditions.