Abstract: A two way hydraulic drilling jar which includes a tubular housing having an interior surface defining an interior bore. A mandrel is provided having an exterior surface. The mandrel is telescopically received within the interior bore of the tubular housing. The exterior surface of the mandrel has an enlarged diameter portion. An annular valve member is provided having a first end, a second end, and an interior surface defining an interior bore. The mandrel extends through the interior bore of the valve member. The valve member is confined with capability of limited axial movement between two shoulders projecting from the interior surface of the housing. The interior bore of the annular valve member receives the enlarged diameter portion of the mandrel in close fitting relation. At least one fluid bypass channel is disposed in one of the valve member and the enlarged diameter portion of the exterior surface of the mandrel.