Abstract: The invention concerns an apparatus for growing cell cultures wherein the cultures are located in at least one liquid nutrient medium and the nutrient medium or media are introduced through at least one pump-driven feed line, and where a gas (oxygen, nitrogen, air or the like) is introduced into the head room above the liquid level of the closed container, the gas pressure being kept constant in the head room, this apparatus being designed in such a manner as to prevent effectively injury to the free cells perforce ejected when evacuating the nutrient media. To that end the invention provides an overflow line communicating with the liquid in the container and terminating outside this container, its free end being located so much above the liquid level in the container that the pressure generated by the liquid column in the overflow line balances the gas pressure in the container head room.