Abstract: A form for a concrete tunnel lining usable behind a tunnel excavator with a traveling shield is made of an inner tunnel-lining sheathing and a form front. The inner tunnel-lining sheathing is divided into a plurality of sheathing segments or rings movable independently of each other with intervening segment-bridging yieldable joints. The form front located between the traveling shield and the inner tunnel-lining sheathing is movable forwardly by the conrete which presses in the annular space formed by the traveling shield and/or the surrounding earth and by the inner tunnel-lining sheathing as well as the form front. An operationally beneficial design results when the inner tunnel-lining sheathing is set up for forward motion of the sheathing segments in the tunnel longitudinal direction singly or in groups one after the other relative to the remaining sheathing segments held or remaining at rest.