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The influence of the 3D frictional crack surface interaction on the frac-ture mechanical parameters as well as on the crack path is investigated numerically.For the solution of the boundary value problem the 3D dual boundary element methodin terms of the discontinuous formulation is utilized. This method is especially suited forcontact problems because it deals directly with the discontinuities at the crack surfaces.The contact problem is solved by the application of a penalty method. Coulomb’s fric-tional law is utilized for the consideration of the dissipative nature of frictional contact.For discrete steps within one load cycle the stress intensity factors are determined by anextrapolation procedure from the stress field. Based on the analysis of a load cycle, thecyclic stress intensity factors are obtained. For the simulation of crack propagation animplicit integration scheme of a crack propagation law implemented in terms of a pre-dictor-corrector scheme is applied. The influence of the crack surface roughness isshown by numerical examples.