Trans-1,4,5,8-Tetranitro-1,4,5,8-Tetraazadecalin (TNAD), a cyclic nitroamine. has been studied with regard to the kinetics and mechanism of thermal decomposition. using thermogravimetry (TG), IR spectroscopy, and pressure differential scanning calorimetry (PDSC). The IR spectra of TNAD have also been recorded, and the kinetics of thermolysis has been followed by non-isothermal TG. The activation energy of the solid-state process was determined by using the Flynn-Wall-Ozawa method. Compared with the activation energy obtained from the Ozawa method, the reaction mechanism of the exothermic process of TNAD was classified by the Coats-Redfern method as a nucleation and nuclear growth (Avrami equation 1) chemical reaction (alpha = 0.30-0.60) and a 2D diffusion (Valensi equation) chemical reaction (alpha = 0.60-0.90). E(a) and ln A were established to be 330.14 kJ mol(-1) and 29.93 (alpha = 0.30-0.60) or 250.30 kJ mol(-1) and 21.62 (alpha = 0.60-0.90).