Waste materials, potentially following their comminution and potentially following their dying or, respectively, preheating, are burned in a cyclone kiln (buring cyclone or, melting cyclone) at extremely high temperatures above 1500.degree. C. with formation of a molten slag low in noxious substances and a hot exhaust gas in which latter the valuable substances and/or noxious substances contained in the waste materials volatilize, whereby dusts enriched with valuable substances on the one hand and, on the other hand, dusts enriched with noxious substances are respectively separately separated out of the exhaust gas by partial condensation.