A fatigue crack growth model for the threshold and the power regimens is presented. The fatigue crack growth rate equation is postulated by identifying the crack growth driving force with the difference between the calculated strain intensity at the crack tip for an ideal material (HRR-type macro solution) and the actual yield strain. The model is based on four micromechanic material parameters: (i,ii) a characteristic slip distance (Neumann's type) and it's statistical distribution coefficient (iii) a crack tip shape parameter, and (iv) a crack growth compliance, which represents the materials response (crack growth) to the above driving force.Since the effective crack tip radius of curvature cannot be smaller than one slip distance, a natural stress intensity threshold value exists, which is statistically distributed.A direct connection is found between the above microscale coefficients and the characteristics of the fatigue crack growth curve; the Paris law coefficients, and the near threshold response.The model is examined through direct comparisons with experimental data for three different metals. Good agreement is found between the experiments and the model is both the Paris and the threshold regimes, including a statistical scatter for very low stress intensities.