Fretting corrosion may be very generally defined as a surface damage that occurs when two solid surfaces are contacted under relatively high loads and with small relative (vibratory) motions. The phenomenon has been recognized by investigators for many years, but even today it is not thoroughly understood. The many names applied to this occurrence are illustrative of a lack of understanding of the subject. Fretting corrosion has also been called “friction oxidation,” “wear oxidation,” “false brinelling,” “chafing,” “bleeding,” “cocoa.” Some difference of opinion exists as to the rôle of corrosion or oxidation in the mechanism of fretting corrosion; some investigators hold that corrosion or oxidation is an integral part of the mechanism while others believe that it is only incidental. Fretting corrosion is not always recognized as such by many users of equipment wherein it occurs, and as a result the steps taken to prevent the damage are not always successful. Numerous excellent studies of the problem have been made in the past and are being continued today by governmental and industrial groups as well as schools and research institutions. ASTM Committee D-2 on Petroleum Products and Lubricants proposed that a symposium on the subject be held in order to present the views and latest work of leading experts in the field to a wide audience so that as many as possible could benefit from the presentation. A further purpose of the symposium was to stimulate future activity on the subject. Technical Committee G on Grease, under the chairmanship of Mr. R. C. Adams, was given the assignment of organizing the symposium.