Fundamental de-chlorination characteristics of Refuse-Derived Fuels (RDF), which were developed for use as a source of thermal energy, were studied by using both practical RDF and simulated RDF. For the simulated RDF polyvinyl chloride (PVC) or NaCl was added as a chlorine source. In the experiments, single pellets of RDF were burned in an electrically heated batch furnace. The de-chlorination efficiency was calculated by analysis of Cl in the residue after combustion. The efficiency obtained was compared with that obtained by chemical equilibrium calculation. HCl was found to be mainly emitted during the volatile matter combustion. The de-chlorination characteristics for PVC addition differ from that for NaCl addition. For the RDF with PVC and Ca(OH)(2) addition, the de-chlorination reaction depends on the furnace temperature, and the optimum temperature is about 923 K. At low temperature the de-chlorination rate is slower than the evolution rate of HCl gas, whereas high temperature, CaCl2, which is produced by the de-chlorination reaction, is decomposed during the char combustion. For the NaCl addition, Cl is not absorbed into a Ca compound. According to chemical equilibrium calculation, NaCl is evaporated as a form of NaCl and Na2Cl2 vapors, and HCl is not produced.