The degradation of benzene, monochlorobenzene and 1,2-dichlorobenzene in aqueous solution by gamma irradiation was investigated. The effect of the irradiated solution composition was studied. The results showed that benzene is more resistant to destruction than chlorinated benzenes. The presence of oxidizing and reducing reactive species and the rapid reaction rates with halogenated benzenes increased the degradation rate of the pollutants. Dechlorination of CB and 1,2-DCB was observed. High performance liquid chromatography (HPLC) and spectroscopy (UV-Vis) were used to monitor changes in the radiation solutions. The final aqueous irradiation products were shown to be a complex mixture of by-products. The addition of scavengers such as methanol and ethanol required larger doses to decompose the pollutants when compared to those solutions with no additives.