Laser beams provide a highly concentrated energy source that can easily be transmitted and manipulated using fibre optics and other optical cOlnponents such as mirrors. Advantages of laser treatment of componentsinclude: lowdistortion of treated parts; the ability to treat specific areas accurately; flexibility compared with, for example, electron beams; and the ability to conduct treatlnent in air or in inert or reactive gases. Apart fr01n cutting and welding, the first application in the Inaterials field was for heat treatment and involved laser surface hardening in the solid state, based on the heating of a thin sUlface layer that was self quenched by the bulk of the cOlnponent. Numerous further treatments have since been developed that involve melting of the surface layer, with or without addition of material, and more recently purely mechanical processes based on the laser shock phenomenon have emerged. The main laser processes that have already been commercialised or are expected shortlyto be so are reviewed. In each case, the principle and some fundamentals, and the characteristics of the treated surface and their influence on mechanical properties are discussed. Specific applications, particularly in the aerospace industry, are then examined. The influence of sUlface dalnage caused during treatment and the ability of laser processing to repair this damage are also discussed.