Abstract: A side entry down-hole pump for oil wells which relies upon gravity rather than suction to receive incoming oil. A pump barrel is plugged at its bottom end and is anchored in the well. A pair of inlet slots in the side of the pump barrel admit oil to a pump chamber formed in the barrel between the inlet slots and the closed bottom end of the barrel. A pumping element is formed by a plunger assembly which includes a cup body carrying a pair of cup shaped seal rings. A pumping string reciprocates the pumping element up and down and provides a flow passage through which oil is pumped to the surface. During upstrokes, the seal rings move above the inlet slots so that oil flows by gravity through the slots and into the pump chamber. Downstrokes effect compression of oil in the pump chamber to pump it through the flow passage and through a check valve which prevents downflow of oil. A pair of discharge slots in the pump barrel relieve pressure created by oil trapped above the seal rings.