In a method for determining the gas volume flow in gas recirculation at a filling station, by means of a thermal throughflow sensor which is installed in the gas recirculation system of a gasoline pump, measurement values are detected, which represent the mass flow of the gas recirculated during refuelling operations from the respective tank of the motor vehicle to be refuelled into a storage tank of the filling station. Furthermore, information on the composition of the recirculated gas is detected, for example by means of a vapor-pressure curve or a thermal-conductivity measurement cell. The mass flow is determined from the measurement values obtained by the thermal throughflow sensor and the information on the composition of the recirculated gas, calibration data being used. This mass flow is converted into a gas volume flow characteristic of the region of the gasoline pump valves of the gasoline pump. The method is suitable for monitoring the gas recirculation system of the gasoline pump with high accuracy.