In friction stir welding (FSW) a non-consumable rotating tool is used to join sheet materials such as aluminium, copper, lead and plastics and even magnesium, titanium and steel on an experimental basis. The welds are made in the solid phase, and their exceptional weld quality, which is superior to that of most fusion welding processes, especially regarding fatigue properties and low distortion, is attributed to the low heat input. Three Scandinavian companies now use the process for the production of large aluminium panels which are made from aluminium extrusions, and several automotive suppliers are already welding impressive pre-production prototypes. Wheel rims, engine cradles, tubular nodes and tailored blanks are the most promising candidates for industrial application in the automotive sector and are at present being developed. Research and commercial FSW machines are now available and include complete installations to weld up to 16m lengths.