ABSTRACT: Premature bearing failures due to subsurface cracks in the vicinity of nanocrystalline material gained particular interest at different applications such as wind turbine gearboxes in the last years. Since the nanocrystalline material appears white after etching with nital under the light microscope, this phenomenon is often referred as white etching cracks (WEC), white etching areas (WEA) or irregular white structure flaking. Although different drivers related to e.g. the bearing material, load conditions or environmental influences are in discussion for causing these failures, it is claimed that the lubricant composition can affect the tendency of a bearing to fail by WEC as well. This talk shows how lubricant chemistry can affect the formation of WEC and how extensive metallographic sectioning and surface analysis tools help achieve better insights into the underlying mechanisms.