Abstract: An anti-reflux syringe includes a syringe barrel defining a chamber for retaining fluid that has an open proximal end, a distal portion, and a barrel extension tip having a passageway therethrough in fluid communication with the chamber. A plunger stem operative of a piston and elastomeric stopper assembly controls the flow of fluid within the chamber. The piston includes a distal piston extension member located distal of the stopper having a male retention body on its outer periphery capable of being retained within a cooperative female retention element in the interior surface of the barrel extension tip. This retention at a point distal of the stopper establishes a predetermined limit to the distal extension of the elastomeric stopper to avoid an undue compression of the same that upon release or withdrawal of the stopper may cause reflux.