The eXtended Finite Element Method (XFEM) has been used in Cast3m tosimulate static and dynamic problems of crack propagation in elastic-plastic materials. Inthe context of non-linear behaviour we used over-integrated elements [3]. Computationof incremental propagation implies an accurate description of physical quantities (stress,strains, internal variables ...) in a limited area around the crack front, specilly when localciteria and inelastic materials are concerned. Then apriori ignorance of the propagationpath, forces us to use a really fine mesh of enriched elements in a rather large zone.Consequently the cost of this method increases drasticly for engineer-sized problems.Thus we decided to develop an adaptative mesh refinement tool, to create a finemeshed zone that will follow the crack front during the propagation, as illustrated on thefigure below. This tool is completed whith the XFEM method and limits the calculationtime with the number of small enriched elements.The procedure used to simulate a crack propagation with the XFEM method coupledwith an AMR tool in Cast3m, will be described. More particularly the presentation focuseson two important steps of this procedure 1) the refinement algorithm for enriched elements.2) the method used to transfer the mechanical fields from one mesh to another betweentwo steps of propagation, and the good properties of this field transfer.The efficency of the method is illustrated by an application case of crack propagationin elastic-plastic media in 3D.