Abstract: The invention relates to a method for producing a gaseous reducing agent for reducing nitrogen oxides in oxygen-containing exhaust gases, especially exhaust gases of internal-combustion engines, the gases being subjected to a selective-catalytic secondary treatment in a catalytic converter, which is characterized by the fact that a solid reducing agent is brought into contact with a liquid heat-carrying agent that has been heated to a temperature in the range of the evaporation temperature of the reducing agent.