Infrared Microscopy is useful for nondestructive evaluation of semiconductor materials and devices. At wavelengths near 1100 nm, silicon and GaAs have good transparency. Therefore, internal defect structures may be observed. Techniques of infrared microscopy and methods of contrast enhancement such as decoration, interference contrast, and fluorescence are discussed. Applications are presented including examples of precipitates in silicon, die attach bond defects, and strain patterns in epitaxial layers and completed devices.