The thermal stabilities of 3,6-dihydrazido-1.2,4,5-tetrazine (Hz(2)Tz) and its salts with diperchlorate [Hz(2)Tz(HClO4)(2)], dinitrate [Hz(2)Tz(HNO3)(2)], bisdintramidate [Hz(2)Tz(HDN)(2)], and bisdinitroimidazolate [Hz(2)TzBim] have been examined and compared to other 3.6-disubstituted tetrazines. The neutral tetrazines exhibited two principal modes of decomposition: elimination of N-2 from the tetrazine ring followed by cleavage of the remaining N-N bond, and loss of the substituent group, in some cases assisted by proton transfer. The salts Hz(2)TzX(2) undergo reversible equilibrium with the parent Hz(2)Tz and HX, thus. in several cases the decomposition rate of the parent tetrazine and the salt are essentially identical.