Decomposition of aqueous dichlorophenols and trichlorophenols was investigated by means of contact glow discharge electrolysis. With the decay of chlorophenols (CPs), the amount of total organic carbon (TOC) in water also decreased smoothly, indicating that carbon atoms of benzene nucleus could be eventually converted to inorganic carbons. And, it was found that chlorine atoms in the CPs were released as chloride ions. As the by-products, oxalate and formate were formed. The chlorine derivatives of 1,4-hydroquinone and 1,4-benzoquinone were detected as the primary intermediates in the initial stage of decomposition of each of CPs. The decay of both CPs and TOC obeyed the first-order rate law, respectively. The apparent rate constants for the decay of CPs increased with the decrease in pKa values of CPs, while those for the decay of TOC were substantially unaffected.