The invention relates to a gas spring which uses a compensating medium acting on a compensating piston in order to compensate the dependence on temperature of its characteristic. According to a first aspect of the invention, a compensating medium (16M) is selected whereof the critical temperature (TK) is between the lower limit temperature (Tlower) and a temperature exceeding the upper limit temperature (Tupper) of the range of operating temperatures of the gas spring (50) by up to 100° C., and the gas spring (50) is designed such that, at an operating temperature (TB) of the gas spring (50) not exceeding the critical temperature (TK) of the compensating medium (16M), the point indicating the state of the compensating medium (16M) lies on or above the vapor pressure curve. According to a second aspect, in order to simplify the structure of the gas spring (50), a single compensating piston (10) which takes the shape of a cup is used and separates the working chamber (1a), the compensating chamber (16) and the restoring chamber (15) of the gas spring (50) from one another.