An injection device including a housing for containing a syringe having a bore extending from an end surface, a needle communicating with the bore through the end surface and a dispensing piston movable in said bore towards said end surface so as to expel the contents of the syringe through the needle, the housing having an opening at one end through which the needle may extend, a resilient member for biassing the syringe and the needle inwardly off the housing, a first coupling element moveable towards said one end so as to move the needle of the syringe out of the opening and to move the dispensing piston of the syringe towards the end surface, a mechanism operable to release the syringe such that the needle moves inwardly off the housing, a drive coupling for extending from said first coupling element to the dispensing piston of the syringe so as to transfer movement of said first coupling element to the dispensing piston wherein the mechanism is triggered to release the syringe and includes components to delay release of the syringe until a predetermined period after being triggered such that it can be ensured that the dispensing piston reaches the end surface before the syringe is released and/or the mechanism includes an inertial mass moveable with the first coupling element and drive coupling and a release member actuable by the inertial mass to release the syringe such that when the dispensing piston releases the end surface of the syringe and the first coupling element and drive coupling stop moving, the inertial mass continues to move so as to actuate the release member to release the syringe.