The rapid progress of the research field of quantum cha's and its applications called for a book that keeps students abreast of the new developments and at the same time provides a solid basis in subjects which form the canon of the field. This book discusses the following topics: Spectral statistics and their semiclassical interpretation in terms of the Gutzwiller trace formula, Quantum cha's and its applications in mesoscopic physics, Spectral statistics and conductance fluctuations and Quantum cha's in systems with many degrees of freedom. The book connects and continues past and present ac.