An experimental study of 3,3'-bis(azidomethyl) oxetane/3-azidomethyl-3-methyloxetane (BAMO/AMMO) and BAMO/ AMMO/TiO2 was performed to investigate thermal decomposition of the copolymer and the effect of TiO2 on its decomposition. Experiments were conducted at 0.1 MPa with heat fluxes of 100 and 400 W/cm(2), delivered by a CO2 laser. Gaseous samples were extracted by quartz microprobes and analyzed in a triple quadrupole mass spectrometer (TQMS). Gas-phase temperature profiles and surface temperatures were measured using the micro-thermocouple technique to investigate gas-phase reaction zones identified by the species measurement. Species measurements revealed that decomposition products of BAMO/AMMO were quite similar to those reported for BAMO and that the addition of TiO2 caused no significant changes in mole fractions of the products, except for an increase in NH3. Product species were indicative of simultaneous decomposition of the backbone structure and side chains. No evidence of gas-phase reaction was found in gas-phase species or temperature profiles. indicating that the reactions are occurring in the condensed-phase or in a near-surface reaction zone. The regression rate was substantially reduced by the addition of TiO2 at a heat flux of 400 W/cm(2). Based upon the species and temperature measurements, it is argued that this reduction is primarily a result of physical, rather than chemical, effects of the TiO2.