The present book covers different aspects of proton conduction: the first part describes chemical and physical parameters necessary for fast proton conduction and proposes a classification of different kinds of proton conductors. Comparison is made with other hydrogen containing materials (metals, graphites). The importance of partial water pressure, the role of defects and surface phenomena are discussed. The second part treats the chemistry, structures and electrical properties of typical materials from hydrogen bronzes to polymers via ice, hydroxides, acid sulphates, layer hydrates, clays,...