CuCl2-catalyzed formation of polychlorinated dibenzo-p-dioxins (PCDDS) from four 2,6 chlorinated phenols was studied in an isothermal flow reactor. Heated gas streams containing oxygen (8%, mole) and 2,6-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol vapor (300 ppmv, each) were passed through 1 cm particle beds containing CuCl2. Two gas velocities, 2.7 and 0.9 cm/s, were studied, as well as effects of varying the duration of experiments. PCDD yields were greatest between 300degreesC and 450degreesC, with 60% phenol conversion to PCDDs observed at low gas velocity. Over a range of conditions for which total PCDD product yields varied by two orders of magnitude, PCDD homologue and isomer distributions varied only slightly, The major PCDD product was 1,2,3,4,6,8-H6CDD, formed from 2,4,6-trichlorophenol and pentachlorophenol, This congener, and other PCDDs formed from the three 2,4,6 chlorinated phenols, are major constituents of incinerator PCDD distributions.