A method for filling or withdrawing from a pressurized gas tank. The tank having a wall having a cylindrical overall shape with dimensions and thermophysical properties that are given and known. The method including the regulation of the flow rate of the introduced or withdrawn gas, and/or of the temperature of the introduced gas, to avoid a situation in which the tank reaches a given high temperature threshold or a given low temperature threshold. The method including a step of estimating, by calculating in real time, at least one tank temperature from: the average temperature of the tank wall, the maximum temperature reached by the tank wall, the minimum temperature reached by the tank wall, and in that the flowrate of gas or the temperature of the gas is regulated depending on the calculated tank temperature.