An attempt is made to correlate some morphological characteristics of pitting cracks with a simple asperity interaction model. The stress field created by a semispherical pressure is combined with the macroscopic Hertzian stress field. For the initiation of fatigue cracks, emphasis is given to two stresses: the maximum range of the superimposed average shear stress over a semicircular area inclined at an angle α to the rolling surface; and the maximum of the superimposed average normal stress over the same semicircular area. Possible mechanisms for initiation of surface pitting are proposed.Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Hartford, Connecticut, October 18–20, 1983