Book excerpt: The development of photosensitive materials in general and photoreactive polymers in particular is responsible for major advances in the information, imaging, and electronic industries. Computer parts manufacturing, information storage, and book and magazine publishing all depend on photoreactive polymer systems. The photo-and radiation-induced processes in polymers are also active areas of research. New information on the preparation and properties of com mercially available photosensitive systems is constantly being acquired. The recent demand for environmentally safe solvent-free and water-soluble materials also motivated changes in the composition of photopolymers and photoresists. The interest in holographic recording media for head-up displays, light scanners, and data recording stimulated development of reconfigurable and visible light sensitive materials. Photoconductive polymerizable coatings are being tested in electrostatic proofing and color printing. The list of available initiators, poly meric binders, and other coating ingredients is continually evolving to respond to the requirements of low component loss (low diffusivity) and the high rate of photochemical reactions.