Experiments with nitrogen torch at atmospheric pressure have been performed in order to identify the role of surface processes in the mechanism of nitrogen transport during nitriding of stainless steel AISI 304. The unusually thick (approximately 175 micrometers ) layers of supersaturated N solid-solution f.c.c. phase have been obtained for 10 min 450 degrees C. Radically different structure have samples treated for 550 degrees C. The scanning electron microscopy (SEM) surface and cross-sectional micrographs reveal that surface topography is indicator of the degree of modification occurring in the nitrided layer. Surface vacancies generated by surface instabilities move deeply into the bulk at elevated temperatures and form highly defected layer with pores and microcracks. The transport of nitrogen in austenitic stainless steel is driven by the fluxes of matrix atoms directed to stabilize surface instabilities. Nitrogen depth profiles simulated on the basis of the model with surface atom relocation process and activation energy 1.1-1.5 eV and including balanced fluxes of atoms in the bulk for relaxation of surface energy are in quantitative agreement with experimental results.