Thermogravimetry has been used to study the kinetics of the thermal dissociation of solidand liquid ammonium nitrate. Model-fitting and model-free kinetic methods have beenapplied to the sets of isothermal and nonisothermal measurements to derive kineticcharacteristics of the processes. The application of the model-fitting method to the isothermaldata has demonstrated that both solid- and liquid-phase kinetics are characterized by asingle activation energy of ∼90 kJ mol-1 and by the model of a contracting cylinder. A model-free isoconversional method has also been applied to isothermal and nonisothermal dataand has yielded an activation energy of ∼90 kJ mol-1, which is essentially independent ofthe extent of conversion. The obtained kinetic characteristics have been assigned to theprocess of dissociative sublimation/vaporization.