Cyclotriborazane (CTB), B3N3H12, is a crystalline white solid, which decomposes above 400 K to hydrogen and a few other products, depending on the reaction conditions. In this work we present investigations of the thermal decomposition of both the neat compound and CTB dissolved in diglyme and tetraglyme. Several thermophysical and analytical methods, such as differential scanning calorimetry (DSC), thermogravimetry (TG), mass spectroscopy (QMS), and B-11 nuclear magnetic resonance spectroscopy (NMR) have been used for this investigation. The decomposition of the neat substance releases 3.1 mol H-2/mol CTB and leads to a polymeric products and borazine. In open vessels, sublimation as a competing process also occurs. The enthalpy of the decomposition process (Delta H-R(s)) has been determined as Delta H-R(s), = -34.0 +/- 2.9 kJ/mol. In contrast to the thermal decomposition of the pure substance, the decomposition in polyethers, such as diglyme and tetraglyme, leads above 370 K to borazine and small amounts of soluble oligomeric borazine species. Also BH3 group containing species are occurring as intermediates. In these systems no precipitation was detected. DSC measurements show for the decomposition in solution several strong exothermic effects. The overall decomposition enthalpy in diglyme is given by Delta H-R(d) = -32.0 +/-2.8 kJ/mol and in tetraglyme by Delta H-R(0) = -48.0 +/- 4.7 kJ/mol. The enthalpy of solution of cyclotriborazane was determined in diglyme and in tetraglyme with the values Delta H-D(d) = -2.1 +/- 0.2 kJ/mol and Delta H-D(t) = -4.6 +/- 0.5 kJ/mol, respectively. (C) 2007 Elsevier B.V.. All rights reserved.