Ion implantation has been successful in producing significant improvements in the wear resistance and fatigue endurance of metals such as steel, titanium, copper and electrodeposited chromium. Models to explain this behaviour in terms of the pinning of mobile dislocations are presented. Friction coefficients are also modified by ion implantation, and in the composite material cobalt-cemented tungsten carbide this effect is very strong, and is accompanied by a reduction in wear. Examples of the range of tools which have been improved by nitrogen ion implantation are given, and the review concludes with a description of the equipment developed for the industrial application of this process.