Temperature-controlled gas cell and thin film laser pyrolysis techniques have been used to investigate the condensed phase thermal decomposition of ammonium dinitramide (ADN). Gas cell experiments have been performed at heating rates of 10(-2)-10(-1) degrees C s(-1) and in a temperature region 20-250 degrees C. Pulsed CO2 laser heating of thin ADN films has allowed heating rates of 10(7) degrees C s(-1) and temperatures of about 630 degrees C to be reached. The thermal decomposition products have been monitored by FTIR spectroscopy. Both experimental techniques show that the primary decomposition products are N2O and NO2. Nitric oxide is produced at a later stage in the reaction. No evidence has been found for participation of dinitramidic acid in the reaction mechanism. The fact that the same initial products are observed over a wide range of temperatures and heating rates shows that this mechanism can be used to model the initial stages of combustion of ADN.