IT is intended to show in this article the magnitude of the weight saving which can be achieved on simple struts. It is necessary for any comparison to derive the weight and shape of the solid or hollow strut theoretically most efficient. This can be done most conveniently using the Calculus of Variations and it will be assumed in all cases that the strut is of such a length that bending stresses predominate at the instant of failure and that the ends of the strut are rotationally free.