The initial decomposition products of 3-nitro-1,2,4-triazol-5-one (NTO) are characterized using laser-induced decomposition of a solid sample. Heating of solid NTO samples is achieved by irradiation with 7 ns pulses of 266 nm laser light while the gas-phase products are detected using 118 nm single-photon ionization in a time-of-flight mass spectrometer. Product translational temperatures and relative product yields are obtained by analysis of time-of-arrival scans. The translational temperature depends linearly on decomposition laser fluence and agrees with the results of a calculation of the temperature rise in the irradiated volume using the heat conduction equation. The relative product yields are used to determine the percent decomposition of NTO as a function of temperature. The temperature dependence of the experimental fractional decomposition is consistent with that obtained from an RRKM calculation of the temperature dependence of NTO unimolecular decomposition. The temperature dependence of the relative product yields is used to identify the initial channels. The initial reaction appears to be bimolecular with a net loss of an O atom to yield nitroso-TO. Early unimolecular reactions include loss of NO2 and nitro-nitrite rearrangement followed by loss of NO.