Abstract: The present invention relates to a needle-less injector having a housing comprising: a chamber defined within said injector for containing liquid to be injected; a liquid outlet for said chamber positioned at the front end of the injector; a dispensing member in contact with the liquid in said chamber and movable in a first direction to reduce the volume of said chamber to cause the liquid contained therein to be expelled through said liquid outlet; an impacting member arranged to strike said dispensing member to cause movement thereof in said first direction; drive means connected to the impacting member for actuating said injector, or permitting actuation thereof, in response to the application of a selected amount of axial pressure, characterized in that the housing is essentially unitary and the chamber, the liquid outlet and the drive means are immobile with respect to the housing, and that the injector comprises a pressure sensor in order to sense the axial pressure, which pressure sensor is connected t