Abstract: The invention provides an infeed structure for a disc type refiner including a body having two passages which at their one ends commonly open from a portion of the body which is adapted to bridge an inlet opening to the interior of a disc type refiner. One of the passages is a material infeed passage and the other a steam vent passage. Incorporated in the portion of the body adapted to bridge the inlet opening to a disc refiner are means, preferably integrated, which in the application of the infeed structure serve to distinctly separate the discharge end of the material infeed passage from the inlet end of the steam vent passage.