Abstract: A dosing device for dispensing very small quantities of liquid includes a variable displacement piston for varying the pressure within a chamber and valves located in inlet and outlet ducts communicating with the chamber. The valves preferably comprise a disc having a circular periphery and including passages therein which are radially spaced from the central portion of the disc. This central portion engages a valve seat to close off the corresponding duct and is preferably rigid to prevent permanent deformation of the disc. The peripheral edges of the disc are received in an annular groove and are free to move radially therein.