An injection device comprises a housing (101) to (104) containing a syringe (24). The contents of the syringe (24) are viewable through a window (14) in the mid-section (102) of the housing. The window (14) is concealed by a slideable shutter (12). The slideable shutter (12) is biased by a bias spring (22) which also biases an internal syringe carrier. Also disclosed is a reversible needle cap which operates initially to cap the front end of the housing and, upon removal thereof, pulls a needle sheath (30) off the syringe needle (26). The cap is designed to be reversible so that, after use, it can be reversed and reconnected to the housing to cover the exposed needle.