This handbook is aimed to deliver an up-to-date account of some of the recently developed experimental and theoretical methods in EPR, as well as a complete up-to-date listing of the experimentally determined values of multifrequency transition-ion spin Hamiltonian parameters by Sushil Misra, reported in the past 20 years, extending such a listing published by him in the Handbook on Electron Spin Resonance, volume 2. This extensive data tabulation makes up roughly 60% of the book`s content. It is complemented by the first full compilation of hyperfine splittings and g-factors for aminoxyl (nitroxide) radicals since 197 by Larry Berliner, a world expert on spin labeling, helping to identify and interpret substances and processes by means of EPR techniques. The book also includes coverage of the recently developed experimental technique of rapid-scan EPR by Sandra Eaton and Gareth Eaton, and a thorough review of computational modeling in EPR by Stefan Stoll, author of Easy Spin. von Misra, Sushil K.