This study examines the effects of chloride on the partitioning and speciation of heavy metal during waste combustion by using simulated municipal solid wastes (MSW). The results indicate that increasing the chloride content of the waste and the combustion temperature may cause the formation of volatile heavy metal compounds, thus increasing metal partitioned to the fly ash and the flue gases. As identified by X-ray diffraction (XRD), speciation is found to be primarily influenced by the reactive affinity of the heavy metals, the types of chlorides, and the metal concentrations in the waste. (C) 1997 Elsevier Science B.V.