Subsurface residual stress measurements were made on SAE 52100 steel inner races from 207-size deep-groove ball bearings in which ΔH (ball hardness minus race hardness) ranged from −1.1 to 3.5 points Rockwell C. These bearings had been run at an inner-race speed of 2750 rpm and a radial load of 1320 lb producing maximum Hertz stresses of 352,000 and 336,000 psi at the inner and outer races, respectively. The residual stress measurements were made in a circumferential direction at various depths below the inner-race running track surface for a total of 19 of these bearings that had been run for nominally 200, 600 and 1600 hr. The measurements indicated that the maximum compressive residual stresses occur in approximately the same ΔH range for which the maximum fatigue lives were observed. Additionally, no relation between running time and residual stress could be determined from these measurements.