Vanadium phosphates exhibit a wide range of structures partly due to the different oxidation states which this metal adopts and the variety of ways in which phosphate tetrahedra and vanadium-oxygen polyhedra can be interlinked. Interest in these compounds arises from the fact that most of them are potentially useful as catalysts or precursors of catalysts for selective oxidations. On the other hand, these systems also have some interest from the point of view of vanadium/phosphate interactions in biological systems.