Abstract: An electrode assembly for a plasmatron, comprising a holder being cooled having a high-heat insert mounted therein in contact with a near-the-electrode zone of an arc at one side thereof and in thermal and electrical contact with the cooled holder at the other side thereof; a chamber formed in said holder between said high-heat insert and cooled holder extending symmetrical to the insert axis and filled with a substance whose coefficient of thermal conductivity is lower than that of the material of the cooled holder, the substance filling the chamber being in constant contact with the high-heat insert.Used as a substance filling the chamber is a gaseous element, and as a high-heat insert is a metal selected from groups IV, V, or VI of the Periodic System, or an alloy based thereon.