Vapors of 1,3,3-trinitroazetidine (TNAZ) were pyrolyzed in a single-pulse shock tube, under high dilution in Ar, over the temperature range 750-1100 K (reflected shocks). The decay of TNAZ and the appearance of the reactive intermediate, NO2, were followed spectrophotometrically at 271 and 405 nm, respectively, in real time via a multiple-pass quartz extension of the shock tube terminus. Samples of the major products that were generated during 1.5 ms residence time and wave quenched were identified and quantitated by GC and FTIR. The unimolecular rate constant (high-pressure limit) for dissociation of TNAZ under our experimental conditions is k(uni) = 10(13.96+/-0.63) exp[(-19900 +/- 1190)/T], s(-1). Successive fissions of NO2 groups were indicated by the time-dependent absorption levels at 405 nm. A gas-phase FTIR spectrum of TNAZ recorded at similar to 110 degrees C provided the missing data for computing the thermochemical parameters for this compound. Then the partition of its decomposition products (minimal free energy) could be calculated for 900 and 1100 K. The observed product distributions differ markedly from those calculated, indicating that the overall reaction is kinetically limited. Several possible reaction pathways at the early stages of the pyrolysis are discussed, and a preliminary reaction mechanism consisting of 46 chemical reactions is proposed. Simulations based on this mechanism agree reasonably well with the experimental results despite uncertainties. Additional work on the pyrolyses of mono- and dinitro substituted azetidines is needed to determine the relative importance of the various dissociation pathways in the present system.