The book addresses many problems of ion exchange processes in LiNbO3, LiTaO3 and KTiOPO4 ferroelectrics and II-VI semiconductor single crystals for integrated optics applications. The authors start with the fundamentals of ion exchange processes in solids (Chapter 1). Chapter 1 can be considered also as an enlarged introduction to the book. Starting with Chapter 2, the general properties of LiNbO3 and LiTaO3 crystals, the methods used to study optical waveguides in these crystals as well as advanced preparation methods of optical waveguides are reviewed. Chapters 3, 4 and 5 are devoted to recent progress in the ion exchange processes in LiNbO3, LiTaO3 and KTiOPO4 crystals, respectively, and Chapter 6 summarizes the main applications of ion-exchanged waveguides in modern integrated optics. Finally, Chapter 7 deals with recently established ion exchange processes in II-VI semiconductors.