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Fatigue strength and fracture mode of shot peened materials depend onthe conditions of the shot peening treatment. As for the fracture mode, internalfracture was recognized frequently, where fish eye pattern was observed on the fracturesurface. Residual compressive stress underneath the surface of the material plays animportant role to these phenomena. Fatigue tests were carried out for shot peenedspecimens under various conditions of shot peening treatments. The site of the originof fish eye has a good correlation with the depth of crossing point from the specimensurface where residual stress changes from compressive stress to tensile one.Theshape of fish eye was influenced by residual stress strongly. The scatter band of S-Nplots has a tendency to become narrow when stress amplitudes at the sites of origin offish eye are used as the stress amplitude of S-N plots.