This thesis studied the effect of microstructure on the fretting fatigue behavior of IN-100. First, fretting and plain fatigue S-N curves were determined over a large range of applied stress at an identical R-ratio and for fretting tests, with a constant contact load. It was found that fretting fatigue reduces the cycles to failure compared to plain fatigue. The half contact width was found for the specimens, the crack initiation angle was found to be 40- and the crack initiation location was at the trailing edge of contact for the fretting specimens. Computational work included finding the stress profile in the contact region using an analytical method and finite element method. The analytical method computed half contact width and was found to be in good agreement with experimental half contact width. The stress profiles produced from each method were compared and found to be in good agreement. The stress state was used to find the Modified Shear Stress Range (MSSR) Parameter.