Abstract: The pressure differential plunger of the present invention is a hollow cylindrical member having an internal bore for the passage of fluid therethrough as the plunger is reciprocated within the barrel. The lower end of the plunger has a tapered or venturi throat leading into the bore to reduce turbulent flow. A ball-type pressure differential valve is mounted within and adjacent the top of the plunger. The cylindrical body of the plunger is configured to be slidably fitted within the pump barrel such that the seal provided by the slidably fitting metal surface of the cylindrical body and the pump barrel are positioned between the valve element and the lower end of the bore. The top of the plunger also has means for connecting the plunger to a conventional sucker rod.