The power requirements for acousto-optic devices increase with wavelength as X2, so it becomes extremely important for infrared operation to have very high figure-of-merit materials available. Potentially important infrared applications include scanners for laser radar, choppers for surveillance satellites, and acousto-optic tunable filters for a variety of systems. Higher efficiency materials are also important as thin films for integrated optic devices, such as the spectrum analyzer, and several bulk acoustic wave-optical waveguide concepts. A large number of materials of the sulfosalt class have been identified as having very desirable acousto-optic properties, and will find use in a number of these applications. More development of these materials is required to make them of suitable quality, and new compositions must be examined to achieve high performance.