A metering valve for an aerosol receptacle, is provided with a valve body having an internal chamber (17) for contact either with the internal face of the valve or with the external face of the valve, a stem (41) provided with closure means (42) and placed partly inside the internal chamber (17) for moving between a closed position in which the internal chamber contacts the internal face of the valve, but isolated from its external face, and an open position in which the internal chamber contacts its external face but isolated from its internal face, and a reservoir (R) able to be filled with the stem in the closed position and emptied with the stem in the open position. The reservoir is on the side of the internal face of the valve, outside the valve body, contacting its internal chamber, and formed by at least one flexible membrane (2).