For at least two decades there has been a considerable growth of interest in the problem of conducting liquids. Initially this was stimulated by the possible technical application of liquid metals as coolants in nuclear reactors, but in the past few years interest has shifted towards a more fundamental understanding of both the structure and electronic properties of liquid metals and alloys. During the same period important progress has been made in the general theory of both the metallic and the liquid state and this has had a great impact on the development of the subject of liquid metals.