The corrosion behaviors of Fe and four commercial steels with different Cr contents were investigated in an oxidizing atmosphere containing HCI at 500～600℃, which simulated the environment to which materials are usually exposed in waste incineration. All the test materials underwent an accelerated corrosion in this atmosphere and small amounts of chlorine could be detected at the metal/scale interface. The corrosion mechanism is discussed on the basis of thermodynamic considerations for the reactions between metals and mixed O-CI gases.