We propose a modified model for the description of crack growth formulated in terms of a probabilistic approach based on a two-parameter Weibull distribution. Unlike the earlier proposal of the authors, in this new model, the applied level of stresses explicitly appears in all deduced equations. The process of crack growth is described by a difference equation fundamental for the proposed model. The efficiency of the method is illustrated by an example of prediction of crack growth and fatigue life for specimens of laser-hardened medium-carbon steel subjected to reversed torsion. The character of fatigue crack growth and specific features of fractographic pictures of the fracture surfaces in the investigated specimens are analyzed.