Abstract: A towing circuit (20) for a hydrostatic travelling drive system with a prime mover, a variable displacement pump (3) and a travel motor (2) supplied thereby, a parking brake (6) arranged to be applied by a brake valve (9) and, optionally, a steering booster (30) and differential gear locking means (40) actuated by a change-over valve (34) has its inlets connected to the travel motor (2) through shut-off valve means (22). A filling pump (4) is connected to supply conduits (7,32) in which the brake valve (9) and the change-over valve (34), respectively, are arranged. Feeding conduits (26,45) provided with check valves open into these supply conduits (26,45). The feeding conduits (26,45) are connected with connecting conduits (21a,21b) governed by the shut-off valve means (22). During towing operation, the travel motor (2) driven by the wheels (1) generates the auxiliary pressures in the supply conduits (7,32) required for the operation of the steering booster (30) and the differential gear locking means (40).