The microstructure of ultrafine-grained fee metals (Al, Al-Mg alloys, Cu and Ni) produced by applying severe plastic deformation (SPD) techniques is Studied by X-ray diffraction line profile analysis. It is found that Mg addition promotes efficiently the reduction of the crystallite size and the increase of the dislocation density in Al during SPD process. In Al-Mg alloys the crystallite size reaches its minimum value at lower strain than the dislocation density suturates. The results also show that the yield strength correlates well with that calculated from the dislocation density using the Taylor equation. (c) 2005 Elsevier B.V. All rights reserved.