This volume contains the proceedings of the Fourth Taniguchi International Symposium on the Theory of Condensed Matter, which was held at Senkari Semi nar House of Kwansei Gakuin Universi y in Sanda-shi, Japan, during the period of 3-8 November 1981. The topic of the symposium was "Anderson rocalization," one of the most fundamental problems in condensed-matter physics. Since Anderson's classic paper was published in 1958, much theoretical and experimental effort has been performed to study the problem of electron localization in a random potential. Quite recently, Abrahams, Anderson,...