In a method for regenerating a nitrogen oxide storage catalytic converter arranged in an exhaust pipe of an internal combustion engine, a constant value is set in a first regeneration phase for the air/fuel ratio λM of the air/fuel mixture fed to the internal combustion engine when a predeterminable triggering threshold value for the nitrogen oxide concentration in the exhaust gas on the output side of the nitrogen oxide storage catalytic converter is exceeded. The first regeneration phase is followed by a second regeneration phase, in which the time rate of change d λM/dt of the air/fuel ratio λM is set as a function of the mass flow of the exhaust gas flowing through the nitrogen oxide storage catalytic converter or as a function of an internal combustion engine operating variable linked with the mass flow of exhaust gas.