The purpose of this study was to examine the strength characteristics of mortar filled steel tubes undergoing axial compressive loading and combined axial compressive and beam loading. The experimental work was restricted to seamless steel tubes and the tests were divided into three series: Series A. Axial compressive loading. Series B. Axial compressive and beam loading combined. Series C. Axial compressive loading of concentric tubes. It was concluded that the axial steel and mortar stresses in the elastic range are determinable by a uniaxial analysis. No satisfactory conclusions were obtained for the inelastic behavior.