Abstract: The invention relates to a vibration damper, especially for damping retraction or extension springing forces on motor vehicles, which includes a pressure medium cylinder (2), in which a piston (3) with a piston rod (3) is axially slidably arranged. The piston divides the pressure medium cylinder (2) into a retraction chamber (5) and an extension chamber (6), in which an electrorheological or magnetorheological fluid is contained as a pressure medium. The retraction (5) and extension chambers (6) are connected with one another at least by a throttle gap (7), in the region of which at least one field force generating element (17) is arranged. At least one further non-return check valve (14) is arranged in a further gap (13) between the pressure medium chambers (5, 6). The invention is characterized in that the length of the throttle gap (7) is divided by a gap intersection or gating point (10) into a first throttle gap section (11) and a second throttle gap section (12).