Abstract: A process for converting a copper sulphide matte and/or a copper sulphide concentrate to blister copper is described which comprises the steps of adding the matte and/or concentrate together with a suitable flux to an agitated molten bath containing molten slag phase and a molten metal phase; injecting by means of a submerged lance an oxidizing gas capable of reacting with the matte or concentrate to form a low sulphur blister copper phase, slag and sulphur dioxide; controlling the injection of the oxidizing gas such that a substantial portion of the gas contracts the blister copper phase; and separating blister copper from the bath. It is possible to obtain an amount of sulphur in the blister copper which is within a factor of two of the equilibrium value for a given percentage of copper in the slag.