A kinetic mechanism was developed for the growth of boron nitride films, including up to 35 species and 1012 gas-phase reactions. For 117 elementary reactions, rate constants are available from published experimental/theoretical data and a code was written to estimate the others using transition state theory. As an example of our approach, we report here results for one of these reactions, BF2 + NF = BF3 + N of presumable importance for the mechanism, using geometries and electronic energies (including their first and second derivatives), calculated ab initio along the minimum energy path. The reaction proceeds in two steps and rate constants were calculated for the temperature range 200-4000 K. (c) 2005 Elsevier B.V. All rights reserved.