The invention relates to a tube assembly for an endoscope comprising a disposable tube that surrounds a working channel and preferably also a flushing channel and fixing means for fixing the disposable tube to the endoscope. Said fixing means have a fixing unit which is used to fix the disposable tube on the distal end of the endoscope in a rotationally and axially fixed manner. The endoscope fixing means also have a guide device which is used to displaceably fix the disposable tube on respective sections of the endoscope that are at a distance from the distal end of said endoscope.