Abstract: A bag forming, filling and sealing machine for producing bag packages with a base or block bottom comprising a forming tube whose lower part has two segments that accomplish a transition from a circular inlet cross section to a rectangular outlet cross section via a square intermediate cross section. As a result of the intermediate cross section, differences in length longitudinally along the jacket lines from the circular inlet cross section to the rectangular outlet cross section of the forming tube are virtually equalized. As a result, bulging and corrugation of the packaging material at the side faces of the bag packages is virtually precluded.