The project aims at developing models of adsorption and reaction at surfaces. The basis is detailed self-consistent calculations using density functional theory with a non-local desorption of exchange and correlation. Models based on the effective medium theory and the Newns-Andersen model are developed to identify the important parameters determining the reactivity of a given system. The theoretical work is closely coupled to experiments on model systems and in industry. The systems studied include clean metals, alloys, transition metal sulfides, and models of enzymes.