This is the second volume in the NATO ASI series dealing with the topic of hydrogen in solids. The first (V. B76, Metal Hydrides) appeared five years ago and focussed primarily on crystalline phases of hydrided metallic systems. In the intervening period, the amorphous solid state has become an area of intense research activity, encompassing both metallic and non-metallic, e.g. semiconducting, systems. At the same time the problem of storage of hydrogen, which motivated the first ASI, continues to be important. In the case of metallic systems, there were early indications that metallic...