The discussion of fatigue damage is generally separated in two domains: Low Cycle Fatigue (LCF) and High Cycle Fatigue (HCF). The transition zone concerns the case of limited endurance, while the unlimited endurance is generally assimilated with HCF. Fatigue failure is the result of complex microscopic phenomena which occur under cyclic loading. However, the principal mechanism responsible for the crack initiation, common to all domains, is the spatial extension of inelastic strains (plastic or viscous) in the grains due to the motion of dislocations. The major difference between HCF and LCF regimes is that inelastic strains develop at the material's mesoscopic and macroscopic scales, respectively. As the underlying mechanics are the same, there should be no reason to have distinct criteria in HCF and LCF. The objective of this paper is to give some further considerations based on dissipation towards a unified method to treat fatigue damage.