A process for the production of a moulding composed of foamed polytetrafluoroethylene by means of an extruder, includes introducing a foaming agent, which brings about foaming, into the polytetrafluoro-ethylene, where the extruder used includes a commercially available extruder, to which a thermoplastically processable, fusible polytetrafluoroethylene is fed, the polytetrafluoroethylene is fed to the extruder together with a foaming agent which has chemical action and which has a decomposition temperature of at least 320° C., and after its discharge from the extruder, the moulding is drawn off in the direction of production without any further measures relating to the foaming procedure.