A gas tension spring contains a cylindrical inner tube which forms a cylinder for a working piston guided in the cylinder in a longitudinally displaceable manner and carrying a piston rod, which is led out in a sealed-off manner. The inner tube is surrounded by an outer tube and forms together with the latter a cylindrical annular space which is fluidically connected to the rod-side cylinder chamber and to the inner space of the piston rod. The said hollow spaces are provided with a common gas filling under pressure. The gas tension spring has a flatter spring characteristic than known gas tension springs and is mounted in the pressureless state. After assembly, it is filled with gas by a cap-shaped closure part slipped onto the outer end of the piston rod. The closure part is held on the piston rod in a positive-locking manner.
