A radial flow valve is disclosed which includes a plurality of flow openings, a first piston and a second piston, the first and second pistons being independently actuable relative to one another, and a sleeve operatively coupled to the second piston, the sleeve adapted to be positioned so as to cover the plurality of flow openings. A method is also disclosed which includes positioning a radial flow valve in a subterranean well bore having an upper zone pressure and a lower zone pressure, increasing a pressure within the valve to a value above the upper zone pressure to release a first piston within the valve and, after releasing the first piston, reducing the pressure within the valve to a value that is less than the lower zone pressure to thereby cause a second piston within the valve to move and thereby permit fluid flow through the valve.