An injection device 1 comprises a plunger (60) for expressing medicament from a syringe (20). An actuation mechanism (40) is arranged in use to provide a biasing force to urge the plunger (60) from a first rearward position to a second forward position to express a dose from the syringe (20). The device further comprises a latch member (50) comprising an aperture (54) through which the rearward end of the plunger (60) extends in its rearward position so as to be retained against the force of the actuation mechanism (40). A trigger (70) is provided for releasing the plunger (60) from the latch member (50). The rearward end of the plunger is provided with an enlarged head (66) and the latch member (50) is arranged to at least partially radially displace such that the aperture (54) may expand to release the enlarged head. The trigger (70) is moveable between (1) a primed position in which it prevents displacement of the latch member (50) and a release position in which it allows displacement of the latch (50).
