Time rates of wear and distance rates of wear are presented as a function of calculated oil film thickness between two cylindrical steel rollers loaded to a maximum Hertz contact stress of 300,000 psi. Wear is divided into a constant wear mode and a transient wear mode depending on the oil film thickness. A negative slope of the curve representing the distance rate of wear versus oil film thickness explains the stabilizing effect on radial surfaces. A positive slope in a narrow range of oil film thickness causes a surface instability due to wear and surface rippling occurs. Transient wear occurs at the thicker oil films. When followed by zero wear rate surface oxide films develop. The total amount worn off during the transient varies greatly with the oil film thickness when using rollers of a given surface finish. Control of oil film thickness by either velocity or viscosity changes due to tempearture produces similar wear effects.Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference held in Chicago, Illinois, October 17–19, 1967.