The mechanical properties under monotonic as well as under cyclic loads of ultrafine-grained (UFG) materials produced either by equal channel angular pressing (ECAP) or by accumulative roll bonding (ARB) are reviewed. Special reference is given to fundamental aspects of the fatigue behaviour of UFG materials. Microstructural investigations after cyclic loading showed that the UFG materials tend to be microstructurally rather unstable. Depending on the material, macroscopic shear banding over larger or smaller scales was noted. Moreover, within the shear bands only slight grain coarsening but a pronounced shape rotation was observed for UFG Al, whereas for UFG Cu a significant dynamic grain coarsening occurring during cyclic deformation was found to be the mechanism responsible for the intense cyclic softening. These microstructural effects are discussed from a more general point of view in order to review the current knowledge on fatigue phenomena of UFG materials and to formulate key features in order to enhance the fatigue properties of UFG materials. Special attention is given to the enhanced strain rate sensitivity found in monotonic tests of UFG materials and its effects on the fatigue lives.