The so called "vario mill" (P4 Fritsch) planetary ball mill has been used to prepare nanocrystalline Fe-10 wt% Ni and Fe-20 wt% Ni alloys from powder mixtures. For both studied alloys, a disordered body cubic centered (BCC) solid solution has been formed after 36 h of milling. The higher the shock power, the larger the lattice parameter of the investigated systems. It has been found that in friction mode process (FMP), the lower the crystallite size, the lower the lattice strain of the prepared alloy. In shock mode process (SMP), the lower the crystallite size, the higher the lattice strain. FMP has been found to induce a soft magnetic behavior for Fe-10% Ni and F-20% Ni alloys. The highest values of coercivity have been found in materials prepared by SMR (C) 2004 Kluwer Academic Publishers.