Abstract The degradation of nitrobenzene using some advanced oxidation processes (O3/UV, O3/UV/H2O2 and O3/UV/Fe(III)) has been investigated. In the combined O3/UV process, the effect of pH and ozone was studied. In the other combinations, the influence of the amount of hydrogen peroxide and ferric ion in the degradation rate and TOC evolution, has been studied. Under our conditions, the combination O3/UV did not improve the degradation rate obtained by ozonation. The best TOC decrease was obtained when the O3/UV process was carried out at low ferric ion concentrations.