This is a revised version of the first edition published in 1991. At the same time, this is a revised version of the Syokabo edition, which was written in Japanese and published in 1993 as a revised version of the original edition published in 1983. Compared with the first edition, the following revisions have been made: a new chapter on electron-electron interaction has been prepared by a new co-author A. Fujimori. The substances in the previous Chap. 4 have been changed, and La-xSrxMn03 substituted for V 0 , which has been exten­ 1 2 3 sively reviewed in Reviews of Modern Physics, Vol. 70, p. 1039 (1998) by M. Imada, A. Fujimori and Y. Tokura. Section 4.6, NiO, was rewritten by A. Fujimori. The other chapters have also been revised by each author to ac­ commodate new developments which have appeared since the publication of the first edition. As a result, the references have been increased from 1088 to 1293, and 83 figures are new or improved. The authors are: N. Tsuda for Chaps. 1, 2 and Sects. 5.1-5.5 and 5.9, K. Nasu for Chap. 2, A. Fujimori for Chap. 3 and Sects. 5.6 and 5.7, and K. Siratori for Sect. 5.8. The authors would like to express their gratitude to many authors and publishers for allowing them to reproduce their diagrams, and to H.K.V. Latsch and C.E. Ascheron for their encouragement to complete this book.