A resource that brings together protein sequence, structure and functional information, including overall chemical reaction and mechanistic data, for structurally defined domain superfamilies. FunTree uses the CATH classification to annotate and analyse super families of enzymes. In particular the relationships between known 3 dimensional structures, associated sequences and the enzyme chemistry is highlighted. This can be used to place structures and sequences in context of their evolution and the range and similarities/differences in the reaction chemistry (both bond order changes and small molecule substructure). In addition it can be used to infer the possible range of reactions of enzyme structures and sequences that do not have a known function as well as indicating other reactions or substrates available to an enzyme that as yet may not have been observed (enzyme promiscuity).