To predict the fatigue lifetime of a P/M component not only the loading history must be considered, but also the porosity distribution, which can influence the material behavior significantly and which is calculated in the first step of the simulation. A model developed for describing the fatigue damage evolution in fully dense steels was adapted to the special situation in P/M materials. On the basis of elastic-plastic fracture mechanics a damage parameter is developed and the number of cycles to failure is linked to the damage parameter by a power-law relation. This model is applied in the second step of the analysis. To demonstrate the potential of the method, the fatigue lifetime of two parts was simulated, a simple fatigue test specimen and a 3D gear wheel.