Transition metal [Mn(II), Fe(II), Fe(III), Co.(11), Ni(II), Cu(II) and Zn(II)] salts of 5-nitro-2,4-dihydro-3H-1,2,4-triaole-3-one (NTO) have been incorporated as ballistic modifiers in composite solid probellants (CSPs) of hydroxyl terminated polybutadiene (HTPB)-ammonium nitrate (AN). The steady burning rate of the propellants was considerably increased by the additives, Zn(NTO)(2) being the most efficient one. The condensed phase thermolysis of such propellants was studied using non-isothermal TGA and DTA and the effect of additives is evident from these studies also. Also, the effect of these additives on the non-isothermal heating of AN from room temperature to similar to300degreesC was studied using TGA and DTA. The additives lowers the decomposition temperature of AN considerably. DTA studies show that the additives alter the phase transition temperatures of AN. Heats of combustion of the modified propellants were found to be higher than for the control one. (C) 2003 The Combustion Institute. All rights reserved.