This study examines degradation of five tertiary polyamines (di- and triamines) in the presence of CO2 or O-2. They were chosen to identify the impact of alkyl chain length between amine functions. Degradation of aqueous amine solutions was evaluated at 140 degrees C under CO2 or air pressure (2 MPa) in stainless steel batch reactors for 15 days. At the end of the run, most degradation products were identified by gas chromatography (GC)/mass spectrometry; amounts of remaining amine and its degradation products were determined with a quantitative GC method. The main degradation mechanisms are proposed, and some structure properties relationships are established.