Since the advent, of railways, the main work in lubrication has been towards understanding the formation of the oil film. The emphasis is now changing. Interest, is concentrated on film breakdown. While hydrodynamic theory can calculate the film thickness between surfaces, it cannot predict the critical, oil-film thickness for failure. This is the task of surface chemistry and metallurgy. In this paper, the factors involved in failure are described, in particular the importance of physisorption and chemical reaction, or chemisorption, is emphasized. A mechanism of scuffing based, on the residence time of molecules is advanced.Presented at the 34th Annual Meeting in St. Louis, Missouri, April 30-May 3, 1979