This volume contains the proceedings of the Eighth Taniguchi Interna- tional Symposium on the Theory of Condensed Matter, which was held at Shima Kanko Hotel in Shima, Japan, 10-13 April 1985. The topic of the Symposium was Valence Fluctuation and Heavy Fermion Systems, one of the most fundamental problems in present-day condensed matter physics. The dilute Kondo problem, which is one of the most typical and unique many-body problems in condensed matter physics, developed recently into the dense Kondo and the coherent Kondo lattice problems in the 4f elec- tron systems. It is accepted now...