The experimental evidence and mechanism of ＇hydrogen spill-over＇ on Pt/WO3 is reviewed and the application of this catalyst system for the evolution of hydrogen, anodic oxidation. hydrogenation and the anodic oxidation of small molecules and impure H-2 is discussed. It is suggested that further work on preparation techniques to ensure the maximisation of Pt/WO3 interfaces and other analogous systems should lead to even higher catalyst activity and applications.