An auto-injector 1 comprising a housing 3 with a syringe 151 slidably received therein, the syringe 151 having a barrel 135 with a piston 157 movable therein and a needle 155 extending therefrom. The piston 157 is further releasably secured to one end of a plunger 111 which is slidably secured within a body 71 in the housing 3 and is operable through a bias provided by a motive source, such as a spring 141. In use, the plunger 111 moves under the bias from a loaded condition to a discharged condition to move the syringe 151 so that the needle 155 extends from a tip at an injection end 7 of the housing 3 and to slide the piston 157 within the barrel 135 to expel the contents of the syringe 151. The plunger 111 is held in the loaded condition against the bias by a detent 91 extending from the body 71 and which is released by operation of an actuator 171 when pressure is applied to the tip 15.
