The method for treating the dust entails the following steps:(a) supplying a combination of dust, a reducing agent and flux to a gastight electrothermic smelting furnace,(b) smelting, reducing and volatilizing certain metals in the smelting furnace,(c) tapping of an inert slag phase and a liquid metal phase from the smelting furnace,(d) continuous removal from the smelting furnace of a gas phase containing chiefly CO-gas, metal fumes, sulphur, chlorides and fluorides together with entrained unreacted dust,(e) further treatment of the gas phase.The process produces an inert slag phase which can be safely deposited in a landfill. The process also allows for recovery of valuable metal components from the dust.