In the five years since the first edition of this book appeared, the field of in- verse scattering theory has continued to grow and flourish. Hence, when the opportunity for a second edition presented itself, we were pleased to have the possibility of updating our monograph to take into account recent developments in the area. As in the first edition, we have been motivated by our own view of inverse scattering and have not attempted to include all of the many new directions in the field. However, we feel that this new edition represents a state of the art overview of the basic elements of the mathematical theory of acoustic and electromagnetic inverse scattering. In addition to making minor corrections and additional comments in the text and updating the references, we have added new sections on Newton’s method for solving the inverse obstacle problem (Section 5.3), the spectral theory of the far field operator (Section 8.4), a proof of the uniqueness of the solution to the inverse medium problem for acoustic waves (Section 10.2) and a method for determining the support of an inhomogeneous medium from far field data by solving a linear integral equation of the first kind (Section 10.7). We hope that this second edition will attract new readers to the beautiful and intriguing field of inverse scattering.