Ultrafine-grained (UFG) and nanocrystalline materials are of great scientific concern on account of their outstanding mechanical and physical properties. A fundamental understanding of the fracture and fatigue properties of such materials is important for their possible application as structural materials. The Severe Plastic Deformation Technique High Pressure Torsion (HPT) was used to refine the microstructure of pure iron and nickel. In connection with various heat treatments sample grain sizes ranging from 10 m to 100 nm were obtained. In the framework of this thesis fracture and fatigue properties of pure iron and nickel materials were characterized by fracture toughness, crack propagation measurements and cyclic tension-compression tests. The mechanical investigations were supported by detailed Scanning and Transmission Electron Microscopy. Experiments were performed to determine the effect of grain size on fatigue and fracture behaviour. As a conclusion distinctive differences between the submicrocrystalline and the microcrystalline grain size were found and discussed with reference to fracture and fatigue.