The thermal decomposition of 2,4-diazido-6-trinitromethyl-1,3,5-triazine, 2,4-dimethoxy-6-trinitromethyl-1,3,5-triazine, and 2,4-diazido-6-methoxy-1,3,5-triazine in a melt was studied by differential scanning calorimetry, thermogravimetry, manometry, mass spectrometry, and IR spectroscopy. The kinetics of these reactions was investigated, and the activation parameters were determined. The gaseous products of the decomposition of 6-trinitromethyl-2,4-diazido-1,3,5-triazine were N2, NO, N2O, CO, and CO2 in a molar ratio of 1: 2: 1: 0.6: 1 and pronounced amounts of NO2. A comparison of kinetic data for the compounds under study indicated that the azide groups in 2,4-diazido-6-trinitromethyl-1,3,5-triazine were thermally more stable than the trinitromethyl group.