Experimental procedures for carrying out fretting fatigue tests using either the proving ring method or a specifically developed servo-hydraulic biaxial rig are described. S-N curves are generated with and without fretting in order to establish the important variables that can affect fretting fatigue and to rank material fretting combinations that should be avoided. The S-N tests and associated metallography indicate that small cracks, typically 0.25–0.5 mm deep, initiate rapidly at only a small fraction of fatigue life. Fracture mechanics and near-threshold fatigue concepts can be used to predict the conditions for continued growth or arrest of the small fretting defects.