The invention concerns an injection device (110) with a housing (112) adaptedto receive a syringe (114) having a discharge nozzle (118) and a plunger(130). There is a trigger and a drive (134) arranged to act upon the plungeron actuation of the trigger to advance the syringe from a retracted positionto an extended position through an opening (150) in the housing. A lockingmechanism (160, 170) is arranged in and moveable relative to the housing. Thelocking mechanism is engaged with the plunger when the syringe is not in itsextended position and disengaged from the plunger when the syringe is in itsextended position. This means that movement of the plunger relative to thesyringe is prevented when, in use, the syringe is advanced from a retractedposition to an extended position. Hence the contents of the syringe are notexpelled from the syringe during advancement form the retracted position tothe extended position. Hence the contents of the syringe are not expelled fromthe syringe during advancement form the retracted position to the extendedposition. The contents are only expelled when the syringe reaches the extendedposition.
