Abstract: The present invention relates to a multipurpose drilling tool that may be cycled between drilling and underreaming operations while situated in a well bore. More specifically, the present invention provides a multi-purpose tool in the form of a housing member comprising a central bore, four extensible underreaming blades and means for attaching a standard drill bit. The ability of the multipurpose drilling tool to cycle between drilling and underreaming modes is provided by means of a piston which is motivated downwardly and rotationally by fluid pressure and is directed by a piston travel guide from a first relaxed position to either a drilling position or an underreaming position. The present invention enables cycling of the tool within the well bore without requiring the removal of the tool and drilling string from a well bore, thus increasing the efficiency of drilling operations.