A numerical analysis was conducted to deduce the Arrhenius-type reaction rates of a reduced reaction model for HAN. The reaction rates were obtained by an inverse-based analysis in a way that minimized an objective function, which consisted of the difference between the calculated concentrations from the numerical model and experimental data as well as the uncertainties in the experimental data. The experimental decomposition process was modeled by applying the species conservation equations to the condensed-phase and the gas-phase regions separately. The experimental data that were used to deduce the rate coefficient parameters were the gas-phase species concentrations observed during thermal decomposition of 13M HAN including HNO3, N2O, NO, and NO2. The energy equation was not considered in the numerical model since measured condensed-phase reaction temperatures were used as input data. The uncertainties in the deduced reaction rates were calculated using the standard deviations of the experimental data. With the best-fit rate constants of the reaction model, the species evolution profiles of 13M HAN were reasonably recovered, and the condensed-phase mass fractions were predicted. The reaction model was applied to the simulation of the species evolutions for solid HAN and HAN-water solutions including 10.7 and 9M HAN. The simulated gas-phase concentrations coincided well with the experimental data, indicating that the proposed global reaction mechanism captured most of the key reactions of HAN. (C) 2003 The Combustion Institute. All rights reserved.