Considering the need for accurate vaporization rates in the propellant combustion models, sublimation and vaporization rates of cyclotrimethylenetrinitramine (RDX) have been estimated over a wide range of temperatures. Simultaneous thermal analysis was carried at various slow heating rates, 5, 10, and 15°C/min, using a coupled TGA/DSC-FTIR system. In the solid phase, the mass loss occurs mainly due to the sublimation of RDX, whereas, in the liquid phase, both vaporization and thermal decomposition play a significant role. The extent of thermal decomposition was estimated using a computational model based on a recently developed detailed liquid-phase decomposition mechanism for RDX. For each of the heating rates, a suitable match between computational and experimental mass loss and species evolution profiles was achieved. As evident from the FTIR data, a major part of the mass loss occurs because of the evolution of decomposition products, such as , , , NO, HCN, , CO, and . Results show that vaporization accounts for 29.6, 34, and 35.9% of the total mass loss for the 5, 10, and 15°C/min heating rates, respectively. Relatively more RDX vaporizes at higher heating rates because of the initiation of the boiling phenomenon at higher sample temperatures.