The temperature-programmed desorption (TPD) of N-2 from a multiply promoted iron catalyst used for ammonia synthesis has been studied in a microreactor system at atmospheric pressure. From TPD experiments with various heating rates a preexponential factor A = 2 x 10(9) molecules/sites and an activation energy E = 146 kJ/mol was derived assuming second-order desorption. The observed dependence of the TPD peak shapes on the heating rates indicated the influence of readsorption of N-2 in agreement with the results obtained for various initial coverages. Simulating the N-2 TPD curves using the model by Stoltze and Norskov revealed that the calculated TPD curves were not influenced by the molecular precursor to desorption. However, the calculated rate of readsorption was found to be overestimated at high coverage compared with the experimental results. A coverage-dependent net activation energy for dissociative chemisorption (E*) was introduced as the simplest assumption rendering the dissociative chemisorption of N-2 activated at high coverage. The best fit of the experimental data yielded E* = (-15 + 30 theta) kJ/mol using only a single type of atomic nitrogen species. These findings are in satisfactory agreement with the parameters underlying the Stoltze-Norskov model for the kinetics of ammonia synthesis as well as with the data reported for Fe(111) single crystal surfaces.