Spectrokinetic analysis by IR spectroscopy was performed on 1.07 m carbohydrazide, (NH2NH)(2)C=O, in a Pt/Ir flow cell with diamond windows. The reaction rate at five temperatures between 503 and 543 K at 275 bar pressure was obtained. A lumped kinetic scheme involving two rate constants is proposed for the conversion of carbohydrazide to CO2 and N2H4. In the first step carbohydrazide decays by pseudo-first-order kinetics (E(a) = 88 +/- 1 kJ mol(-1), 1n(A/s(-1)) = 18). Delta S-double dagger = -108 J mol(-1) K-1, which is consistent with the involvement of H2O in the cleavage of the C-N bond. The main intermediate thus formed is proposed to be the hydrazinium salt of hydrazacarboxylate, which can exist in equilibrium forms. This intermediate decomposes in the second stage of the reaction to N2H4 and CO2 with global Arrhenius parameters of E(a) = 57 +/- 1 kJ mol(-1) and ln(A/s(-1)) = 10 for the initial 10-15% of conversion to CO2. At higher percentage of conversion, the rate of formation of CO2 greatly accelerates, which suggests autocatalysis. The catalyst is proposed to be CO2 by its effect on the hydrogen ion concentration.