Modem mechanical surface optimization processes today go beyond simple empirical techniques. Typical examples are presented, demonstrating the possibilities to increase lifetime and strength of components by mechanical surface treatments. A focal point is the relation between materials properties and microstructures created by near surface plastic deformations and their consequences on cyclic deformation, crack initiation and crack propagation during cyclic loading. In this context, also the stability of microstructures and residual stresses in surface layers is discussed.