Abstract: An injection syringe for injecting a fluid into the arterial, venous, muscular or cavity structures of a patient via subcutaneous, percutaneous, intravascular and other types of injections comprises a hollow syringe body, a passageway at a distal end of the syringe for passage of fluid into and out of the syringe and a substantially open proximal end for receiving a plunger assembly. The plunger assembly includes a movable plunger assembly. A moveable plunger cooperates with the syringe body and the proximal end of the syringe to define a fluid chamber of variable volume in fluid communication with the passageway. Actuating means actuates movement of the plunger. An elastomeric barrier cooperates with the plunger and the open end of the syringe to define a sterile chamber between the actuating means and the fluid chamber to prevent passage of fluids from the fluid chamber to the actuating means and the passage of contaminants from the open end of the syringe in the fluid chamber.