Experimental and chemical modeling studies of H2/N2O/Ar, H2NH3/N2O/Ar, and H2/N2O/NO2/Ar flames are performed to test and refine a detailed chemical mechanism developed in our laboratory. This mechanism consists of 103 reactions and 22 species, and is denoted VS-modified-2. Flame temperatures are measured with a coated, thin-wire thermocouple and by OH and NH laser- induced fluorescence (LIF), whereas species concentration profiles of H2, NH3, N2O, N2, H2O, NO, O2, NH and OH are recorded using molecular beam/mass spectrometry, LIF, or both. The experimental species concentrations are compared to those generated with PREMIX, a 1D, laminar, flame code, using the measured temperature profile and the VS-modified-2 mechanism as input. Overall, laminar, flame code, using the measured temperature profile and the VS-modified-2 mechanism as input. Overall, the PREMIX calculations predict very well the major, species concentrations throughout each flame. For the H2,N2O,Ar flame, the postflame O2, OH, and NO concentrations decrease by approximately 90, 45, and 35 percent, respectively, with the addition of approximately 4 percent NH3. This decrease is predicted rather well by the PREMIX calculations, which show a decrease in O2, OH, and NO by approximately 90, 55, and 40 percent respectively. The shapes of the modeled O2, NO, and OH profiles for the H2/N2O/NO2/Ar flame are in excellent agreement with those observed experimentally. The modeled OH profile even predicts an observed peak at approximately 3 mm above the burner surface. This peak is attributed to the competition between the NO+H equals NO + OH reaction, which produces OH, and the H2 + OH equals H2O + H reaction, which consumes it. Rate and sensitivity analyses of the above-mentioned flames are presented discussed.