Abstract: Procedure for preparing hot groundwood from wood chips, wherein a chip stream is conducted into a pressurized steaming chamber, where the chips stay a few minutes and are heated to a temperature higher than 100.degree. C., and from the steaming chamber through a sluice feeder into a hot grinder of enclosed construction, i.e. the stage I grinder, when the pre-ground groundwood is conducted through a separating cyclone into a stage II grinder, the groundwood derived herefrom being conducted towards further treatment steps. The pre-ground groundwood is conducted from the steam separating cyclone through a sluice feeder into the stage II grinder. The stage II grinding is carried out in a hot grinder of enclosed construction.