An injection device has a locking mechanism that in an engaged position prevents removal of a protective cap 111 and in a disengaged position prevents forward motion of a syringe 114 and its carrier 127 but permits removal of the cap from the injector housing (112, figure 1a). This assists in preventing damage to the syringe prior to actuation of the injection device. Two buttons 171 located on the front end of the injection device are depressed to move locking arms 173 out of engagement with the cap. The same motion brings abutment surfaces 179a on the arms into engagement with the syringe carrier to prevent it from moving forwards. The arms may extend through and so secure a sliding sleeve (119, figure 2a) and thereby prevent triggering of the injection mechanism whilst the cap is being removed.
