Possible application of the TiO2/UV-VIS photocatalytic process in the destruction of nitrogen-containing malodorous compounds was evaluated. Pyridine (C5H5N), propylamine (C3H7NH2) and diethylamine (C4H10NH) were photodegraded in the presence and in the absence of oxygen. Degradation of nitrogen-containing organic compounds was confirmed by mass balance taking into consideration NH4+ and NO3- ions trapped at the TiO2 surface. Photocatalytic deactivation was observed in all cases. On-line mass spectrometry was used to identify byproducts in the gas phase formed during the degradation process. GC-MS analysis of the dichloromethane-extract of aqueous species leached from the surface of deactivated catalyst, as well as pre-concentration in a Tenax column were used to identify intermediates in the gas phase. These byproducts are considered to be the major ones responsible for deactivation of TiO2. (C) 2001 Elsevier Science B.V. All rights reserved.