An injection device (110) is disclosed comprising a housing (112) adapted to receive a syringe (116) where the syringe is movable along a longitudinal axis of the housing (112) between a retracted position and an extended position. A syringe carrier (127) supports the syringe (116) as it is advanced. A cap (111) is removably located over an exit aperture (128) of the housing (112) and a locking mechanism (170a, 170b) is adapted, in an engaged position, to prevent removal of the cap (111) from the housing (112). In a disengaged position the locking mechanism (170a, 170b) permits removal of the cap but prevents movement of the syringe carrier (127) towards the exit aperture (128).
