An electronic ballast for at least one gas discharge lamp (LA), preferably for a fluorescent tube, having a rectifier circuit (2) connectable to a supply voltage source, a smoothing circuit (3) connected to the output of the rectifier circuit (2) for generating an intermediate circuit voltage (UZ), and an inverter (4), fed with the intermediate circuit voltage (UZ), to the output of which a terminal for the load circuit (5) containing the lamp (LA) is connected, and an overvoltage monitoring device which monitors the supply voltage (U0) delivered to the electronic ballast, whereby in the event that the supply voltage exceeds a predetermined nominal value (Ui,max), an optically or acoustically perceptible warning signal is issued.