An improved understanding of NOx formation at high pressures would be of considerable utility to efforts to develop advanced combustion devices. A combination of theoretical and modeling studies are implemented in an effort to improve the accuracy of models for the prompt NO process, which is the dominant source of NO under many conditions, and to improve our understanding of the role of this process at high pressures. The theoretical effort implements state-of-the-art treatments of NCN thermochemistry, the interrelated CH + N-2 and NCN + H kinetics, and the kinetics of the NCN + OH reaction. For both reaction systems, we implement high level ab initio transition state theory based master equation simulations paying particular attention to the role of stabilization processes. For the NCN + H kinetics we include a treatment of inter-system crossing. The modeling effort focuses on exploring the role of pressure and prompt NO for premixed laminar flames at pressures ranging from 1 to 15 atm, via a comparison with the available experimental data. Additional simulations at higher pressures further explore the mechanistic changes at the pressures of relevance to applied combustion devices (e.g., 100 atm). (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.