Nearly neutral aqueous solutions of 22 organo-chlorine compounds undergo photodegradation (λ>250nm) catalyzed by paratungstate A anion, [W 7 O 2 4 ] 6 - , which was obtained by adjusting pH levels of the Na 2 WO 4 solution to 6-7. In each case the organic substrate was decomposed through dehalogenation. The rate of Cl - formation strongly depends on substrates. The photochemical redox reaction between paratungstate A and substrates proceeds via precomplexation. The Langmuir-type dependence of the reaction rates on the concentration of substrates provides a promising method for the dechlorination of alkyl- and aromatic-chloride compounds such as ClCH 2 CH 2 CH 2 Cl, C 3 H 7 Cl, and C 6 H 5 CH 2 Cl.