The sputter coating process is reviewed, with particular emphasis on applications in the mechanical sciences. In addition to principles and methods of d-c and RF sputtering, the techniques of reactive, bias, and getter sputtering are described. Special attention is given to the plasma discharge as it relates to the achievement of high deposition rates and large substrate areas. The current state of development of sputtering equipment is examined from the point of view of its influence on coating properties and applications to production. Future prospects are discussed. It is concluded that significant increases in both deposition rate and area of coverage can be expected for d-c sputtering systems operating with cylindrically symmetric geometries. Less spectacular improvements are projected for RF sputtering.