Fretting fatigue testing usually arises as the result of some failure which it is imperative to overcome either by a modified design or application of some surface treatment. In such cases the test rig is usually designed to replicate the actual situation as closely as possible (e.g., a press fit or riveted joint) with environmental conditions as near to those occurring in practice (e.g., high temperature or a marine atmosphere). In laboratory testing the purpose is much wider, and usually entails, for instance, the assessment of different materials for their susceptibility to fretting damage, or the effect of variables such as clamping load, amplitude of slip and frequency, in particular environmental conditions. The type of fatigue test is very relevant (i.e., whether the response is the same in rotating-bending, push-pull or torsion, and whether in the latter two cases, a mean stress is applied). The nature of the contact is also material (i.e., whether it is flat-on-flat or cylinder-on-flat, or even crossed cylinder). How is the clamping stress to be applied? If by a proving ring, then the pressure can change according to whether the debris is trapped or can escape; a dead weight method might be preferable. Surface finish and residual stress are factors which must be taken into account. All these matters must be considered in devising a recommended testing procedure.