Abstract: A hydropneumatic hammer operated by a reciprocal action of a percussive piston and a directional control valve, comprising a piston having steps of larger and smaller diameters separating the interior of a piston chamber intended for admitting said piston into four chambers, a first chamber communicating by way of a first passage with a pressure line, the second chamber being defined by a step of middle portion of said piston connecting to a discharge line, the third one being defined by a step formed on an upper portion of said piston, and the fourth one defining a gas chamber separated from the third chamber by a seal retainer, a valve chamber intended for admitting a valve system, being arranged parallel to said piston chamber, a passage for converting a pressure line of fluid or oil into a discharge line and connecting said valve chamber with the second chamber, a passage for returning an exhausted fluid or oil being converted into depressurized condition after working, a first passage intened for deliver