A process for preparing chlorine by catalytic gas-phase oxidation of hydrogen chloride over a fixed catalyst bed is disclosed that includes: making available a feed gas stream I with hydrogen chloride and an oxygen-containing feed gas stream II, feeding the feed gas stream I, the feed gas stream II, and, if desired, a recycled stream Ia with hydrogen chloride, an oxygen-containing recycle stream IIa, and a recycled stream III into an oxidation zone and oxidizing hydrogen chloride to chlorine in the presence of a catalyst present in a fixed bed to give product gas stream IV having chlorine, unreacted oxygen, unreacted hydrogen chloride and water vapor, and taking the recycled stream III from the product gas stream IV, without further treatment, and recirculating it to the oxidation zone, leaving a product gas stream IVa.