Lanthanum2containing cathodes are an attractive alternative to thorium tungsten cathodes be2 cause of their low work function and their comparatively low operating temperatures. A La2Mo carbonized cathode was described, which had a high thermionic emission; it was made up in a similar way to the Th2W cathode, but possesses high emission values. The thermionic tube equipped with La2Mo carbonized cathode was designed for comparison with Th2W cathode tube. It was experimentally verified that La2Mo cathode has higher thermionic emission effectiveness and its operating temperature is about 200 ℃lower than that of Th2W cathode. The emission current density of La2Mo wire satisfies for electron tubes as Th2Wfilament. A stable e2 mission current has been obtained with La2Mo carbonized cathode tubes for more than 1 800 h. From the re2 sults it is clear that the emission stability of La2Mo cathode satisfies the requirements for the replacement of Th2W filament.