Seven previously published global kinetic measurements for thermal decomposition of the energetic compound 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO) report Arrhenius activation energies ranging from 40.7 to 120.4 kcal/mol. To resolve this large discrepancy, two potentially dominating processes (sublimation and thermal decomposition) were isolated and their kinetics determined. For sublimation E(a) = 25.8 kcal/mol, In (s(-1)) = 29.2 (isothermal at 0.002 atm); E(a) = 28.6 kcal/mol. In A (s(-1)) = 31.3 (nonisothermal at 0.002 atm). Decomposition kinetics on semiconfined NTO (20 atm pressure) by flash-heating with T-jump/FTIR spectroscopy yield E(a) = 87.1 kcal/mol and In A (s(-1)) = 74.8. From these data and selected, evaluated, previous measurements, the kinetic constants for decomposition alone are E(a) = 78-87 kcal/mol and In A (s(-1)) = 67-78. Smaller values of the Arrhenius parameters reported previously are shown to result predominantly or partly from sublimation.