The components arrangement and control unit of a hydro-pneumatic slow active suspension system is described. Adaptive control strategy for slow active system is used. The gains are selected basis on the suspension working space. Experimental results of the performance of a hydro-pneumatic slow active suspension with adaptive control fitted in quarter vehicle test rig are presented. Performance of a slow active suspension system with and without adaptive suspension is compared. A mathematical model of a quarter car model for a hydro-pneumatic slow active suspension including adaptive control is developed. Then theoretical results are compared with experimental measurements on a test rig. The slow active suspension system with selectable control gains which are chosen according to the input conditions car offer further improvements in ride comfort compared with slow active system with constant control gains.