Compounds rich in nitrogen are attracting much scientific interest because of their high energy content. Given this interest, it is desirable to be able to describe accurately the combustion mechanism and kinetics of HN3, the smallest, high-nitrogen compound. We report a combined experimental and modeling study of neat and HN3-doped H-2/O-2/Ar flames. We employed thin-wire thermometry and hydroxyl (OH) laser-induced fluorescence (LIF) to measure the flame temperatures and molecular beam-mass spectrometry, LIF, or both, to measure the species concentrations. We assembled a detailed chemical mechanism containing 24 species and over 100 reactions and tested it by comparing our experimental profiles HN3, H-2, O-2, H2O, N-2, NO, NH, and OH to those predicted by the PREMIX flame code. Our model predicts well the species profiles, except for HN3 and NO. Rate and sensitivity analyses reveal that the HN3 + OH = N-3 + H2O reaction is important in HN3 consumption and NO production, and we provide a revised rate expression for this reaction that is consistent with our experimental results.