Fretting corrosion—a surface damage occurring between two closely fitting surfaces subject to slight vibrational movement—has caused trouble in machinery ever since the first closely fitting machined parts were put together. It is something different from ordinary wear or rusting of the usual chemical nature, and it is not always recognised as fretting corrosion by users of equipment in which it occurs. ‘Friction oxidation,’ ‘wear oxidation,’ ‘false brinelling,’ ‘chafing,’ ‘bleeding’ and ‘cocoa’ are some of the names that have been applied to the phenomenon. One of the results of work carried out by the Mechanical Engineering Research Laboratory of the D.S.I.R., briefly described in CORROSION TECHNOLOGY, May 1954, is that it is possible to correlate the degree of damage with such variables as total number of oscillations, load or atmospheric humidity. In the United States, too, much work has been done on fretting corrosion and ways of combating it. So that as many as possible could benefit from this research, the American Society for Testing Materials organised a Symposium in which leading experts gave their findings. The Symposium has recently been published as a booklet. Here are shortened versions of two of the papers presented.