We review a selection of recent research work on III-nitride materials, limiting the scope to bulk properties and quantum well structures. The different stages of development of the compounds AlN, GaN and InN are illustrated, with reference to the electronic properties demonstrated so far. The important alloy systems AlxGa1-xN and InxGa1-x have quite different properties, still not understood in detail for high Al and In contents, respectively. Some important unresolved issues are highlighted, and possible future directions of the materials development are indicated. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.