A high degree of resistance to plastic deformation at the contacts between rolling bodies and rings is required in bearings used for equipment that must be quiet running. It is shown that, within practical bearing design limits this resistance is primarily a function of material structure variables that affect the elastic limit. Hardness, as measured by Rockwell or Diamond Pyramid methods is a primary variable, but in itself, an inadequate measure of this resistance. A test method is described giving good correlation with conditions causing plastic deformation of bearings in applications. The effects of residual stress, surface conditions and contact configuration are discussed. It is shown that bearings with substantially improved resistance to plastic indentation are obtainable by the use of appropriate heat treatment.