This paper reviews the bending fatigue endurance limits reported in the literature for carburized steels. Almost an order of magnitude difference in fatigue limits (210-1950 MPa) is reported. The reasons for this wide range are not clear because of the complexity of interactions between the microstructural, testing and manufacturing systems associated with carburized components. In well characterized specimens, two types of microstructures and fatigue crack mechanisms associated with moderate and high levels of fatigue performance have been identified and are described here. Finally, the effects of selected engineering parameters on the measurement of bending fatigue limits are discussed. The need for more complete experimental characterization of fatigue performance is stressed as a critical step to produce consistent bending fatigue performance at the upper end of that attainable in carburized steels.