Total carbon (TC), carbonate carbon (CC) and total organic carbon (TOC) were determined in bottom ash, filter dust and flue gas of Swiss municipal solid waste (MSW) incinerators. The highest TOC load was found in the bottom ash (2–3 g kg-1 MSW), followed by the filter dust (0.1–1.0 g kg-1 MSW) and the flue gas (0.05–0.3 g kg-1 MSW). The composition and behaviour of the bulk of TOC in these products is not yet known. In order to minimize the risk of leaching organic substances as well as metals due to biological, chemical and physical reactions of the products of incineration in a landfill, it is suggested the incineration process be optimized towards complete combustion.