Friction welding has emerged as a reliable process for high-production commercial applications@ with significant economic and technical advantages. Professor Wang@ in his interpretive report@ provides us with an objective view of operating theory@ process characteristics@ advantages and limitations. Of particular interest is his comparison of friction welding with the two principal types of machines@ inertial and continuous-drive. Data are included on the weldability of a variety of similar and dissimilar metals and alloys@ which show the importance of frictional characteristics and high temperature ductility. There is an obvious need for further development work on a number of important metal combinations having marginal weldability. It is the hope of the Interpretive Reports Committee that this document will stimulate further research and development so that this relatively new welding process will achieve its true potential