Abstract: An adjustable flow regulating valve has a flexible apertured diaphragm which coacts with a fixed conical needle to provide a gradually variable effective flow controlling orifice area to compensate for changes in a supply fluid pressure. As the supply fluid pressure changes, the aperture of the flexible diaphragm moves relative to the apex of the needle to reduce or increase the effective orifice area which determines the regulative flow rate. The position of the diaphragm aperture relative to the needle is manually adjustable by rotating an adjustment collar on the valve housing to vary the amount of movement of the diaphragm required to engage the aperture with the valve needle. The diaphragm may also be carried by a spring balanced inner sleeve which allows relative sliding movement between the flexible diaphragm and the needle. The amount of force required for engagement is determined by the strength of compression springs at each end of the sliding sleeve set by the adjustment collar.