In the present investigation the experimental and theoretical flexural and compressive behavior of short tubular steel columns filled with plain concrete and fiber-reinforced concrete (FRC) was examined. For a given length of the members, the effects of different geometry and dimensions of the transverse crosssectionrn(square and circular) were investigated. Constituent materials were characterized through direct tensile tests on steel coupons and through compressive and split tension tests on concrete cylinders. Load-axial shortening and load-deflection curves were recorded for unfilled and composite members. Finally, simplifiedrnexpressions for the calculus of the load-deflection curves based on the cross-section analysis were given and the ultimate load of short columns was predicted.