Process for controlling the fuel supply in a fuel cell system having a fuel cell stack, comprising: determining a first input value by measuring a parameter which is representative of the electric current produced by the fuel cell stack, determining a fuel-supply adjustment value in response to the determined first input value through a previously determined assignment between the measured parameter and the fuel-supply adjustment value, and supplying fuel in accordance with the determined fuel-supply adjustment value, (i) wherein prior to the determination of the first input value it is checked whether there is a lifetime of the fuel cell stack and if this is the case: a lifetime correction value is determined in response to the determined lifetime, and the fuel-supply adjustment value is determined in response to the determined first input value and the lifetime correction value, or (ii) wherein prior to the determination of the first input value it is checked whether a tank exchange has been carried out with a corresponding time span during which the fuel supply was interrupted, and if this is the case: a tank-exchange correction value is determined in response to the determined time span, and the fuel-supply adjustment value is determined in response to the determined first input value and the tank-exchange correction value. determining a first input value by measuring a parameter which is representative of the electric current produced by the fuel cell stack, determining a fuel-supply adjustment value in response to the determined first input value through a previously determined assignment between the measured parameter and the fuel-supply adjustment value, and supplying fuel in accordance with the determined fuel-supply adjustment value, (i) wherein prior to the determination of the first input value it is checked whether there is a lifetime of the fuel cell stack and if this is the case: a lifetime correction value is determined in response to the determined lifetime, and the fuel-supply adjustment value is determined in response to the determined first input value and the lifetime correction value, or (ii) wherein prior to the determination of the first input value it is checked whether a tank exchange has been carried out with a corresponding time span during which the fuel supply was interrupted, and if this is the case: a tank-exchange correction value is determined in response to the determined time span, and the fuel-supply adjustment value is determined in response to the determined first input value and the tank-exchange correction value. (i) wherein prior to the determination of the first input value it is checked whether there is a lifetime of the fuel cell stack and if this is the case: a lifetime correction value is determined in response to the determined lifetime, and the fuel-supply adjustment value is determined in response to the determined first input value and the lifetime correction value, or a lifetime correction value is determined in response to the determined lifetime, and the fuel-supply adjustment value is determined in response to the determined first input value and the lifetime correction value, or (ii) wherein prior to the determination of the first input value it is checked whether a tank exchange has been carried out with a corresponding time span during which the fuel supply was interrupted, and if this is the case: a tank-exchange correction value is determined in response to the determined time span, and the fuel-supply adjustment value is determined in response to the determined first input value and the tank-exchange correction value. a tank-exchange correction value is determined in response to the determined time span, and the fuel-supply adjustment value is determined in response to the determined first input value and the tank-exchange correction value.