Heterogeneous photocatalysis in the presence of semiconductor oxides is a fast advancing field of research especially for the oxidation for organic pollutants in water or air. The photoassisted degradation of aromatic heterocycles (pyrrole, imidazole, pyrazole, isoxazole, oxazole and thiazole) and N-containing alicycles (pyrrolidine, 4-butanelactam and 5-pentanelactam) was examined in liquid-solid dispersions of TiO₂ Degussa P25 (100 mg) with the aim of ascertain the fate of the N atom. The initial solution (0.1 mM, 50 mL) was irradiated with a medium pressure Hg lamp (2 mW·cm^-2, 310-400 nm. Complete mineralization of the aromatic heterocycles was attained within ca. 1 h of UV irradiation in acidic (pH 3), near-neutral (pH 6.0–7.6), and alkaline (pH 11) media. Mineralization kinetics were not appreciably influenced by the presence of acid but were slower in alkaline media. N-alicycles were photomineralized more slowly than the aromatics. The former could be mineralized in acidic and near-neutral media in less than 2 h, but not in alkaline media in which they were not mineralized even after 3 h of irradiation. The final products obtained were in all cases CO₂, ammonium and nitrate ions, along with sulfate anion in the case of thiazole. N₂ gas was also obtained for the photo-oxidation of pyrazole. The molar amount of NH₄⁺ /NO₃^- formed after long irradiation time was closely related to the chemical structure, however, the ammonium amount was in nearly all cases significantly greater than nitrate. Mineralization of isoxazole produced mostly nitrate; probably because of the presence of the N-O function.