This volume presents an outstanding collection of state-of-the-art methodologies for quantifying free radical and antioxidant analytes in tissue and body fluids using experimental models and in vitro procedures. These user-friendly and easily reproducible techniques cover the essential tasks, including radical generating systems, direct measurement or trapping of reactive radical species and acute-phase proteins, and measurement of metabolic intermediates derived from the oxidation of lipids, proteins, and nucleic acids. There are also methods for the determination of vitamin, enzymatic, and water-soluble antioxidants, as well as of essential micronutrients and cofactors. The techniques take advantage of new instrumentation and technology—probes, photon counting, chemiluminescence, and caged compounds, with an emphasis on HPLC—and are adaptable to a wide range of applications. The laboratory-tested free-radical assays described here in detail will illuminate the study of both primary and secondary oxidative stress and contribute significantly to our understanding of the many disorders associated with this process.