A syringe assembly comprising: a barrel for containing one or more medicaments, the barrel having a front outlet for allowing the expulsion of said one or more medicaments from the said barrel through said outlet; a first stopper disposed in the barrel and axially moveable therein and defining a first volume in the barrel axially forwards of the first stopper and a second volume in the barrel axially rearwards of the first stopper; a second stopper disposed in the barrel axially rearward of the first stopper and axially moveable therein, the second stopper providing a fluid tight seal at a rear end of the second volume; a first plunger rod connected to the first stopper and extending axially rearwardly through the second stopper, the second stopper sealingly engaging with the first plunger rod but permitting axial sliding of the first plunger rod therethrough; and a second plunger rod connected to the second stopper, so as to axially move the second stopper when the second plunger rod is axially moved; characterised in that the first stopper has a two way valve that is moveable between a sealing configuration and an open configuration to selectively put the first volume in fluid communication with the second volume, the two way valve being moveable from the sealing configuration to the open configuration by an increase in fluid pressure in either of the first and second volumes (16,18); wherein the first plunger rod is axially moveable so as to axially move the first stopper and pressurise either of the first volume and second volume causing the two way valve to move into the open configuration and fluidly connect the first volume and second volume. a barrel for containing one or more medicaments, the barrel having a front outlet for allowing the expulsion of said one or more medicaments from the said barrel through said outlet; a first stopper disposed in the barrel and axially moveable therein and defining a first volume in the barrel axially forwards of the first stopper and a second volume in the barrel axially rearwards of the first stopper; a second stopper disposed in the barrel axially rearward of the first stopper and axially moveable therein, the second stopper providing a fluid tight seal at a rear end of the second volume; a first plunger rod connected to the first stopper and extending axially rearwardly through the second stopper, the second stopper sealingly engaging with the first plunger rod but permitting axial sliding of the first plunger rod therethrough; and a second plunger rod connected to the second stopper, so as to axially move the second stopper when the second plunger rod is axially moved; characterised in that the first stopper has a two way valve that is moveable between a sealing configuration and an open configuration to selectively put the first volume in fluid communication with the second volume, the two way valve being moveable from the sealing configuration to the open configuration by an increase in fluid pressure in either of the first and second volumes (16,18); wherein the first plunger rod is axially moveable so as to axially move the first stopper and pressurise either of the first volume and second volume causing the two way valve to move into the open configuration and fluidly connect the first volume and second volume.