AbstractComposite slabs are now one of the most popular methods of steel frame floor construction in the world. This article describes the history of their development with special reference to the research undertaken to predict their behaviour. The essential nature of the system is that the profiled steel sheeting acts as both a form and reinforcement to the final concrete slab. The use of the sheeting as a form is similar to its use in roofing and cladding when wind and snow are the predominant loads; however, there are sufficient differences to make the design of composite deck profiles unique. The exact nature of the bond between concrete and steel is, in the author's opinion, still not well understood and is the subject of much international research activity. However, it will be concluded that the continuing effort in research in this area is of little practical benefit to improving deck spans as in most situations the slab end support conditions are such as to allow fully composite behaviour.