Abstract: A device and method for removing nitrogen oxides from the exhaust gas from lean-burn internal combustion engines, e.g., diesel engines used in motor vehicles, includes a feed for a reducing agent, an NH3 sensor for measuring the NH3 concentration in the exhaust gas, and an exhaust pipe with NOx reduction catalytic converter. The arrangement configured to feed in reducing agent includes a control circuit for quantitatively continuously controllable supply of reducing agent to the exhaust gas, the control variable of the control circuit being the NH3 concentration measured by the NH3 sensor, and the guide variable of the control circuit being an NH3 concentration value which may be predetermined as a function of the operating point of the internal combustion engine. The NOx reduction catalytic converter is divided into at least two parts which are separate from one another and are arranged in series in the direction of flow of the exhaust gas.