The idea for this book originated from an International Conference on Mag netic Structures in Superconductors organized by John R. Clem and the author at Argonne National Laboratory (ANL) in September of 1973. Large parts of the book evolved from lectures given to graduate students at the University of TUbingen during the past three years. It is the purpose of this book to provide an introduction to the many features of magnetic flux structures in superconductors and to discuss the this field. Here, in addition to the static proper recent developments in ties of magnetic flux structures, the time-dependent phenomena represent an important subject including flux flow and the transport effects in supercon ductors. Throughout the book the emphasis is placed on the physical phenom ena and the experimental results. We do not attempt a general introduction to superconductivity. Except for a brief discussion of the Ginzburg-Landau theory, with respect to the theoretical developments we only give an outline and refer to the original papers or other reviews for the detail of the calculations. The book is intended for researchers and graduate students interested in the subject of magnetic flux structures in superconductors. It may serve as supplementary material for a graduate course on low-temperature solid state physics. During recent years technological applications of supercon ducting materials are becoming increasingly important. Here the static and dynamic behavior of magnetic flux structures playa distinguished role. The book may be helpful for people envolved in these engineering aspects of superconductivity.