Hydro-pneumatic spring is a gas string with hydraulic force transmission. It comprises a plunger-cylinder assembly and a reservoir connected with the cylinder. It is provided with means for a substantially constant liquid supply and with a discharge throttling opening that varies with the position of the plunger in the cylinder. The plunger is supported in the cylinder by means of hydrostatic bearings which employ the supply and the discharge pressure of the liquid flow through the spring.