Abstract: A pilot-operated, pressure-loaded, movable diaphragm-type gas-flow regulator valve is shown which is used in flow control applications. A regulator body internal port arrangement interconnects two independent throttling mechanisms in series. Two throttle plates are located within the regulator valve body relative to an inlet chamber and an outlet chamber. A movable diaphragm is positioned relative to a throttle plate by a separate pilot control system to vary the area of throttle plate exposed to flow, and thus, the flow rate of the regulator valve. The throttle plates each have drilled flow apertures which control flow through the valve. Smaller flow apertures are opened before larger flow apertures as the valve diaphragm lifts, thereby ensuring stability at low-flow conditions, while providing high capacity at maximum diaphragm lift.