Abstract: A gas operated, plunger lift type pump for use in a subterranean well conduit which extends from a pool of well liquids to the surface comprises a tubular plunger slidably and sealingly mounted in the well conduit and defining a fluid flow passage through the tubular body. An annular valve seat is fixedly mounted within the tubular body and an axially shiftable valve head is engagable with the valve seat to prevent fluid flow through the fluid passage. The valve head is biased to an open position by a surface applied trapped fluid pressure which approximates the hydrostatic pressure existing in the well at the liquid level to which the plunger is permitted to descend, and is further retained in the open position by a latching collet. As the plunger rises in the well due to the gas pressure existing below the plunger, it will raise the fluids trapped above the plunger to discharge through vertically spaced discharge ports.