This paper describes the quasi-static and fatigue performance of hybrid bridge girders composed of cellular FRP bridge decks and steel girders. The FRP bridge deck is connected adhesively to the steel girders and acts as the top chord of the hybrid section. Compared to a reference steel girder, the stiffness and quasi-static load-carrying capacity of the hybrid girders were considerably increased due to composite action between the FRP decks and the steel girders. Failure due to quasi-static loading occurred in the FRP decks during yielding of the bottom steel flanges. The adhesive bond between the FRP decks and the steel girders showed no signs of damage due to fatigue loading. The results of the investigation showed that the well- established design method for steel-concrete composite girders with shear stud connections can essentially be used for the design of such FRP-steel girders. The principal modifications necessary for design are proposed. [All rights reserved Elsevier]