The formation of HCl from inorganic chlorides, NaCl and CaCl2, was studied under simulated municipal solid waste incineration conditions. Experiments were conducted with NaCl and CaCl2 particles of 75-125 mum in diameter, which were placed in a gas flow type tubular reactor in the temperature range of 623-1023 K, in an atmosphere of N-2 containing 2.5-15 vol% CO2 and 2.5-15 vol% H2O. It was found that HCl was not generated from NaCl below 723 K, and that CaCl2 started to release HCl in a CO2-H2O-N-2 mixed gas at around 623 K. The amount of HCl emitted from NaCl and CaCl2 was increased with the increase in temperature as well as the concentrations of CO2 and H2O. Based on a SEM/EDS observation of the distribution of C, O and Cl elements on the surface of reacted sample and the quantitative analysis of the amount of C by a CHN analyzer, it was found that NaCl reacted with CO2 and H2O to produce Na2CO, and HCl. Similarly, HCl was emitted by the carbonation of CaCl2 with CO2 and H2O to produce CaCO3 at a temperature lower than 923 K. On the other hand, the emission of HCI from CaCl2 occurred by the oxidation of CaCl2 with H2O to form CaO at a temperature higher than 923 K.