The paper gives results of a study of the formation of mechanism of polychlorinated dibenzofurans (PCDFs) and polychlorinated naphthalenes (PCNs), with graphite and polycyclic aromatic hydrocarbons (PAHs) as starting carbon sources and copper chloride as catalyst. Polychlorinated dibenzo-p-dioxins (PCDDs) were minor products. The homologue distribution from graphite has octachloro-dibenzofuran (O8CDF) and octachloro-dibenzo-p-dioxin (O8CDD) as main products, while that from PAH were sensitive to the catalyst and reaction temperature. It was suggested that PCDFs and PCNs can be released directly from the carbon sources and that their isomer patterns from perylene and benzo(ghi)perylene, respectively were similar to those from some fluid bed incinerators. The yield of PCDFs from perylene was higher than from PAH, phenol, and activated charcoal, which implied that perylene may play an important role for PCDF formation in these fluid bed incinerators. A dechlorination model succeeded in predicting the consistent isomer patterns from most of the municipal waste incinerators.