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Shot-peened titanium alloy Ti-6Al-4V and nickel-based super alloy IN100 were subjected to plain and fretting fatigue under cylinder-on-flat contact condition at room temperature. Measurement of compressive residual surface stress from shot-peening before and after fretting showed relaxation, which was significant in IN100 and near the contact surface. The fretting fatigue life of IN100 did not improve significantly due to shot-peening, while there was considerable improvement for Ti-6Al-4V and relatively less relaxation of the residual surface stress. Further, fretting had a relatively more detrimental effect on the fatigue performance of Ti-6Al-4V than in the case of IN100. A critical plane-based fatigue crack initiation model, a modified shear stress range parameter, was computed from finite element analysis for two levels of residual surface stress relaxation: no relaxation and complete relaxation. This analysis suggested that not only crack initiation but also propagation should be considered to characterize fretting fatigue behavior of shot-peened specimens; however, it showed an appropriate trend with the measured fretting fatigue life and agreement with several other experimental observations.