This book collects most of the expertise available throughout the world on the instrumentation for the characterization of hypersonic flows. The fundamental requirements are reviewed and the necessity for low uncertainties is pointed out, especially for code validation and the assessment of real gas effects. The various techniques available are essentially non-intrusive and are based on optical diagnostics. Such is the case for flow visualization by the Schlieren technique, holographic interferometry, electron beam fluorescence and laser induced fluorescence. The possibilities of all these techniques (including CARS, laser velocimetry and spectroscopy) are discussed in detail, since they provide the most interesting parameters, such as temperature, concentration and velocity. The methods for measuring thermal flux in models are also discussed, the emphasis being on IR thermography. The book will be of interest to specialists in the hypersonic domain as well as to those involved with wind tunnel testing since it reveals all the possibilities associated with the most up to date techniques of aerodynamic investigation.