The experimental and analytical behavior, strength and stiffness of floor diaphragms constructed with steel-deck-reinforced concrete was investigated in this study. As part of the research, 23 full size experimental diaphragms were tested in a reversed cyclic manner on a cantilever test frame. Experimental parameters that were varied included steel deck type and thickness, fastener type and number, diaphragm thickness and aspect ratio. Expressions to predict strength and initial stiffness, which were first developed in a previous phase of research at Iowa State University, were modified to reflect the results of this study;Edge force distributions, which were related to the load applied to the diaphragm, were used in the predictive equations. These force distributions were developed by means of nonlinear finite element analyses, in which the fasteners and deck-to-concrete interface were modeled with discrete nonlinear force-displacement elements. Predictive strengths and stiffnesses generally showed good agreement with experimental results, with the predictive stiffness values being more scattered than the strength values when compared to the experimental specimens;A design methodology was developed, which incorporated steel deck manufacturers' responses pertaining to existing design methods and system configurations currently in use. As a part of the design recommendations, the use of steel-deck-reinforced concrete diaphragms in seismic design applications are discussed.