Thermal techniques are attractive for materials characterization. They provide sophisticated contrast mechanisms and fast, non-contact investigation of large inspection areas. Recent progress in the development of infrared cameras is the key for a wide variety of new applications. In particular, active thermal techniques provide useful information about thermal properties and related quantities as well as geometrical and structural information. "Active" thermography means that, for the purpose of testing, heat is deposited at the surface of the test object or generated within the test object. The surface temperature is monitored as a function of time during or after stimulation. Thermal quantities are determined from the infrared frame sequence. With "Passive" thermography, the temperature of an object is imaged without additional thermal stimulation. The current chapter presents thermographic NDE methods for detection of delaminations, cracks and corrision damage. Particular focus is set on the new thermographic NDE method called Mechanically Induced Dissipated Heat Analysis - MIDA. This method is employed for fatigue damage characterization.
