Ion implantation, with doses in the range 10 16 to 10 18 ion cm ร 2 , modiยฎes the surface properties of many metallic and ceramic materials. Whilst gas ion beams are currently employed extensively, metal ion implantation (MII) systems have been developed based on the vacuum metal arc and a brief review of these systems is presented. Examples of industrial applications are given using, primarily, Mo ions which harden the surface of steel, increase its corrosion resistance and lower the coecient of friction of the alloyed (or implanted) zone, IZ. Extending well beyond this zone, a dislocation network is developed which hardens the material in depth. Termed the long-range eect, this occurs in alloys and in low ductility materials such as TiN. Microstructural studies of TiN coatings after MII are presented together with a model for the development of this eect. The results show that the stress ยฎeld in TiN made by PVD is modiยฎed by implantation but no eect on the grain structure is found, whereas in TiN made by CVD the residual stress is not changed but growth of ยฎne grains within the original grain structure is observed.