The invention relates to a method for adapting an injection valve characteristic curve of a controlled fuel injection valve for an internal combustion engine, said curve reflecting the reference injection behaviour, to alterations in the actual injection behaviour caused by ageing. According to said method: during an operating mode of the internal combustion engine, which does not require an injection of fuel, the injection valve is intermittently controlled in accordance with a control period, said mode alternating with a period of no fuel injection, i.e. at least one working cycle with injection-valve control follows or precedes a working cycle without injection-valve control; at least one respective RPM value of the internal combustion engine is detected for the controlled working cycle and for at least one of the working cycles without control; a differential between the detected values is calculated and said differential is used to correct the characteristic curve.