This series of lectures will start by considering those definitions suitable for calculating the stress/strain quantities needed for estimating multiaxial fatigue strength of real mechanical components. Subsequently, those pivotal ideas which should always be borne in mind when designing components against fatigue will be briefly summarised, with this being done by mainly considering uniaxial and torsional fatigue situations. By taking as a starting point the above concepts, the way of using the Modified Wöhler Curve Method will then be investigated in depth, by focusing attention on both the high- and the medium-cycle fatigue regime. An attempt will also be made to show the existing links between the Modified Wöhler Curve Method and physical reality. Finally, the procedure suitable for applying this approach to estimate fatigue damage both in notched and in welded components will be considered in great detail.