The rates of thermal decomposition of 2,2',4,4',6,6'-hexanitrostilbene (HNS) and its deuterated derivatives have been determined using isothermal differential scanning calorimetry. These studies were conducted at different temperatures in the range 596-620 K over the first 25% of the liquid-state decomposition where the reaction follows apparent first-order kinetics. In comparative studies, using HNS with deuterium at either the olefinic or aromatic sites, only small kinetic isotope effects (k H /k D =1.05 and 0.92, respectively) were observed