a hydraulic setting tool for use with a packer having expandable anchor means for anchoring the packer in a well bore , a conduit to permit flow through the packer , and a slidable valve positioned in the conduit having an open lower position and a closed upper position . inner and outer tubular portions are telescopically interengaged with the inner portion receiving a slidable mandrel . the tool conduit is connected to the inner sleeve with a shearable tension collar , the mandrel passing through the collar and into the conduit for engagement with the valve . annular pistons are provided between the inner and outer sleeves and between the mandrel and the inner sleeve . a flapper valve is pivotally attached on one side to the inner sleeve for sealing the top of the mandrel . pressurization of the inner sleeve via tubing string from which the tool and the packer are suspended pressurizes the annular spaces beneath the pistons thus forcing the inner sleeve as well as the mandrel upwardly to set the tool . such upward movement of the inner sleeve breaks a seal at the lower end thereof to permit depressurization of the annular space below the mandrel piston which forces the mandrel downwardly . a lock ring locks the mandrel in its lower position to permit further operation of the valve with the mandrel .