Rolling contact bearings are precision mechanical components of many machines, that are produced of high quality alloy steel and manufactured according to strict standards. However, their service life can not be exactly predicted, since it suffers from a large variation, reaching a ratio of 20:1 between the extreme values. Prevailing failure theory of these bearings is based on the fatigue life of the solid components, caused by oscillating high level stresses. This book considers the damaging effect caused by the liquid phase , too. Cavitation of the lubricant causes high local impacts upon implosion of vapor filled cavities. Further on these repetitive impulsion results in pitting of the surface. Presence of water enhances the appearance of cavitation of the lubricant and shortens the bearing service life considerably. It is recommended to dehydrate the lubricants during the entire bearing service life.