A device for regulating the flow rate in the tube, e.g. in infusion- and transfusion assemblies. The flow rate can be regulated by twisiting a portion of the tube by means of a twisting device. The tube comprises at least along the portion of its length which is intended to be twisted a plurality of separate or communicating flow passages (26). Between said flow passages there are provided distance members (12) arranged about or forming an inner core in the tube about which the tube is twisted and which reduces compression of the tube. When the tube is twisted the free space between said distance members is gradually reduced in the twisted cross-section of the tube and by that the flow is reduced.