1,2-Chloronitrobenzene, 1,4-chloronitrobenzene, 2,3-dichloronitrobenzene and 3,4-dichloronitrobenzene in aqueous solution were irradiated in the presence of TiO2 with wavelengths λ > 290 nm. Due to the attack of oxygen containing radicals a fast reaction of these stable compounds was observed. Chloronitrophenols and chlorodinitrobenzenes in minor amounts were determined as intermediate products. Continued irradiation leads to total degradation.