The factors that determine fretting fatigue damage of a given material pair are relative slip between the two surfaces in contact, shear stress at the interface, and tensile stress that forces the crack, once started, to grow. Three types of test are described: a biaxial loading test for interlocking joints, a uniaxial tension-compression test, and a three-point bending test. It is concluded that the latter is sufficient for most purposes besides having low cost and simplicity.