The selective non-catalytic reduction of nitric oxide with ammonia has been investigated experimentally using a perfectly stirred reactor. In a temperature range from 1000 to 1450 K, a set of experimental runs has been performed to investigate the influence of increasing the partial pressure of all the reactants simultaneously. No kinetic limitation to the efficiency of the process due to the high partial pressures of the reactants has been found. This can provide interesting information about the effect of an overall pressure increase on all the reactions involved apart from the three-body ones. Comparison with several detailed kinetic models previously presented in the literature evidenced that these models are not able to represent correctly the process behavior in the conditions investigated. One of these has been properly modified in order to reproduce the experimental data so as to provide an effective tool for process simulation in a wide range of operating conditions.