Electron Paramagnetic Resonance (EPR) spectroscopy, also sometimes termed Electron Spin Resonance spectroscopy, has manifold potential uses in biochemistry and medicine. The paramount importance of EPR spectroscopy applied to biological tissues and fluids is that it identifies the changes in redox processes that contribute to disease. Innovations made possible by the introduction of spin labels, probes, and traps made EPR spectroscopy ever more applicable to biochemistry and medicine, to the point where in vivo studies are being carefully considered. This book discusses spectra of many tissues and bodily fluids, and the quantitative nature of paramagnetic centres in both normal individuals and patients suffering from a variety of diseases. Special attention is given to the EPR examination of bio-molecules, such as enzymes, polypeptides, vitamins, lipids, and hydrocarbons, which play an essential role in human activity.