Abstract: A cell cultivation container with screw cover, where the zone of the mouth portion of the container adjacent the edge of the mouth has a greater diameter than the more remote zone and is constructed with at least two inwardly protruding, axially extending projections, and where the screw cover has an inner skirt with an outer annular bead which in the fully closed position of the cover is in sealing engagement with the inner wall of the narrow zone of the mouth portion of the container, while in partly unscrewed position of the cover the bead is only in contact with the inwardly protruding, axially extending projections. Hereby the cross-sectional area of the communication passages between the interior of the container and the surroundings formed by partial unscrewing of the cover will remain constant, even if the angle of turning of the screw cover varies within wide limits.