THE RECOVERY OF BROMINE AND/OR IODINE FROM THE REACTION PRODUCTS OF OXYDEHYDROGENATIONS OF HYDROCARBONS IN WHICH BROMINE AND/OR IODINE SERVES AS A CATALYST, WHEREIN THE REACTION PRODUCT LEAVING THE REACTOR IS TREATED WITH AN AGUEOUS AMMONIA SOLUTION TO WHICH HAS BEE ADDED AN AMOUNT OF HYDRAZINE SUFFICIENT FOR THE REDUCTION OF THE ELEMENTARY CONSTITUENTS. THE AQUEOUS PHASE IS SEPARATED AND THE BYPRODUCTS CONTAINING BROMINE AND/ OR IODINE SEPARATED IN THE WORKING UP OF THE ORGANIC PHASE ARE BURNT AND OXYGEN-CONTAINING GASES AND THE GAS FROM THE COMBUSTION IS SCRUBBED WITH AN AMMONIA SOLUTION CONTAINING HYDRAZINE.