Abstract: In the case of an opening device for an open-end spinning machine, the rotating opening roller is arranged in a housing with a prevailing vacuum and has one front side which is exposed to the free atmosphere. In the area of this front side the opening roller is sealed off against the housing by means of a labyrinth seal. The labyrinth seal starts in the area of a peripheral combing structure of the opening roller with a first sealing gap and ends with a second sealing gap in the free atmosphere. The sealing gaps are formed by cylindrical collar surfaces of the opening roller and corresponding hollow cylindrical countersurfaces of the housing. In addition, the collar surfaces are provided with fly repulsing notches, whose direction of effect is such that the fly is repulsed at the first sealing gap towards the combing structure and at the second sealing gap, repulsed towards the free atmosphere. The front side of the open roller exposed to the free atmosphere is not covered by a lid.