Abstract: A process for the uninterrupted manufacture of plastic film tubing by the blowing up of a continuous film tubing by means of an extruder-injector, including an inner cooling of the extruded film tubing using a gaseous cooling means initially in a liquified condition introduced inside the film tubing. The cooling medium is converted into its vaporous or gaseous condition through evaporation before being purged. The cooling medium is introduced inside the film tubing in its liquified state in such a manner that up to a reversing point located above the nozzle tip of the device, an upward coolant stream occurs in the center of the inner space of the tubing, from which stream liquid and/or solid coolant particles are carried and kept in suspension. At the reversing point the coolant stream fans out radially after which the cooling medium falls back down in an opposite direction along the wall of the film tubing toward the coolant outlet.