A double-acting pump having two cavities, each of which is divided into an operating chamber and a working chamber by means of a respective movable partition wall. Each of the operating and working chambers is provided with a valve-controlled inlet and outlet for a gaseous driving medium and a pump-transported liquid working medium. A movement transmission device extends between the movable partition walls and transmits movement of one partition wall to the other and vice versa. This movement transmission device includes a spring element for compression and expansion in the movement transmission direction such that a distance between the partition walls is variable as one partition wall can move independently of the other wall responsive to relative gas pressure in the operating chambers.