The destructive oxidation of pentachlorophenol in alkaline aqueous solution has been attempted with tetraoxoruthenium species as catalysts and hypochlorite as the terminal oxidant. The product solution contained no pentachlorophenol. Only traces of chlorinated compounds which could be extracted with dichloromethane were present. Measurements of the quantity of base and of hypochlorite added to the reaction mixture indicated that the oxidation did not proceed to completely to carbonate, but rather to unidentified compounds with an average carbon oxidation state of about three. Oxidation with peroxodisulfate indicated that only two-thirds of the chlorine was present as ionic chloride in the product solution. In contrast, oxidation with permanganate, in the absence of ruthenium, led to the complete oxidation of pentachlorophenol and to release of all of the chlorine as ionic chloride. Qualitative rate measurements were made with the pH-stat technique. Some experiments were also conducted with 2,4,6-trichlorophenol, p- chlorophenol and phenol. Attempts to oxidize both phenol and pentachlorophenol at various ruthenium-containing electrodes in either basic or acidic solutions were unsuccessful.