Carburised steels are largely used in the gears industry to improve the wear resistance of parts. However, it is well known that shot peening, which creates compressive residual stress, increases the fatigue strength of materials. Combining these two treatments should therefore improve both the fatigue flexion strength and the fatigue contact strength. Several specimens were treated in an industrial furnace, and it was demonstrated that it is possible to obtain two retained austenite contents (23% and 37%) under industrial conditions. The specimens were shot peened under three conditions. In the first part, we show the influence of the initial austenite content on the final residual stress and austenite levels after shot peening. The different residual stress distributions, obtained after the three shot peening treatments, are compared. The results of the fatigue flexion and fatigue contact tests should allow the optimum combined treatment to be defined (carburising + shot peening).