The pitting fatigue of a wide range of heat-treated carburizing steels has been investigated. The effects of compositions conforming to 1024, 8620, 4620, 4027, 2048, 4419, 4817 and 9310 at two levels of case carbon content were studied in lubricated concentrated contact. Different microstructures were produced in the 4817 and 9310 steels by combination of case carbon level and subzero treatments. Testing was carried out on geared roller test machines.Pitting fatigue was found to be dependent on microstructure rather than steel composition. As long as the steel possessed sufficient hardenability to avoid transformation products, then fatigue life is not markedly different. It appears that the presence of retained austenite can improve pitting fatigue resistance.