This work presents the supercritical water oxidation (SCWO) of quinoline, a nitrogen-containing organic compound found in pharmaceutical wastewaters, to products that are more readily biodegradable. The effects of the operating variables, namely process temperature, stoichiometric ratio of oxidant to organic, residence time and system pressure were studied in order to optimise quinoline removal efficiency and to investigate the fate of carbon and nitrogen after oxidation. Hydrolysis experiments undertaken in the range 480-650 degrees C showed no significant degradation of quinoline. The present study confirmed that, as an alternative to incineration, the process is fast and effective in treating quinoline in water, converting it into primarily carbon dioxide (CO2), water (H2O) and nitrogen gas (N-2) and to a lesser extent ammonium ions (NH4+). Temperature was shown to be the primary variable in the complete destruction of quinoline and TOC reduction, upon operating at around 250 bars. Essentially, complete quinoline removal was observed above 575 degrees C and complete TOC removal was obtained at 650 degrees C, where CO2 was the main reaction product. (c) 2006 Society of Chemical Industry.