An injection device comprises an elongate housing (10), a removable cap (66), a syringe (12) disposed in said housing and having an internal piston (20) to express a dose from a needle (16) at its front end and a shroud element (24) movable forwardly relative to the syringe to shroud the needle after use. A trigger button (52) is biased rearwardly by means of two integral forwardly extending sprung arms (58). The arms have cam surfaces (60) which ride over respective abutments (62) inside the rear of the elongate housing (10). In use, forward movement of the trigger button (52) is initially prevented by means of two rearwardly extending locking arms (64) which extend back from the rear end of a cap (66).
