The present invention provides a needle-free injection device for delivering a medicament under pressure into an animal or human. The injection device includes an actuating device comprising: a gas tight chamber a piston and rod assembly slidably received in the chamber and movable between a forward position and a rearward position a gas charge in the chamber for urging the piston and rod assembly to the forward position means for moving said piston and rod assembly against said gas charge into the rearward position and a trigger for releasably retaining the piston and assembly in the rearward position. Also provided is a method and kit for using the device to administer a liquid through the skin of an animal or human.
