An external anode electron tube having improved conductive cooling means. A hermetically sealed tube envelope is disclosed having a relatively massive annular, generally cup-shaped metallic external anode having a plurality of spaced, annular projections, and a ceramic tubular envelop member hermetically sealed to the ends of the anode projections. An annular, metallic mounting flange is also disclosed having a plurality of spaced sections, each section having a surface coplanar with a surface of each other section. A disc-shaped ceramic header is further disclosed positioned in spaced relation within the annular flange. The header has a plurality of terminal pins projecting therethrough.