Recycling of waste streams saves resources as well as land space. It is however important to find the most suitable treatment solution in order to optimize the conversion of the waste into useful products and maximize the energy yield, while minimizing secondary waste generation. The processing conditions applied in pyrometallurgical reactors are commonly most suitable for treating various types of inorganic as well as organic wastes. The article discusses the treatment of various types of wastes such as residues from the metallurgical industry and plastics. The available recycling technologies and practices as well as potential pyrometallurgical solutions will be reviewed. The experiences of some non-confidential pilot and demonstration projects carried out by MEFOS in the past 10 years using various kinds of reactors for waste treatment will be highlighted. These projects include: - treatment and recycling of EAF and BOF dust - reduction of valuable metals such as V and Cr from steelmaking slags - stabilization of fly and bottom ashes by a DC furnace with a hollow electrode - destruction of hazardous liquid chemical wastes by injection them in a metal bath.