Abstract: A method of high voltage treatment for a cathode ray tube having a neck including one end closed with a stem and housing an electron gun and stem pins for a focus electrode, and other electrodes of the electron gun, establishes a high pressure gas atmosphere around the neck, and establishes a voltage which is sufficiently higher than the operating voltage of the cathode ray tube between the stem pins when the high pressure gas atmosphere. In order to prevent a creeping discharge due to the voltage applied to the stem pins, the temperature of the neck is maintained above the temperature of said high pressure gas atmosphere during the voltage application. In an alternative method, the dew point of the high pressure gas atmosphere is set at, at most, 25.degree. C.