A process for carrying out an optionally catalyst-assisted hydrogen chloride oxidation process by means of oxygen is described. The process comprises single- or multi-stage cooling of the process gases and separating off of unreacted hydrogen chloride and water of reaction from the process gas, drying of the product gases, separating off of chlorine from the mixture and recycling of the unreacted oxygen into the hydrogen chloride oxidation process, at least some of the heat content of the product gases being used for recovery of heat and at least some of the coldest gas streams being used for cooling in the process.