The fatigue growth of surface flaws in both smooth and notched round bars subjected to rotary bending was numerically simulated by means of a two-parameter theoretical model proposed by the first author. The stress intensity factor distribution along the crack front was needed in order to apply the model. Therefore, finite element analyses and the superposition principle were used to determine such a distribution for a wide range of crack configurations and any position of the flaw with respect to the bending moment axis. The results related to rotary bending are compared to those related to pulsating cyclic bending, and a qualitative comparison is made with some data reported in the literature.