Abstract: A programmed action hypodermic syringe includes a syringe barrel having at least one pin protruding into the bore of the barrel. A plunger is adapted to travel through the bore and has, on its exterior surface, at least one longitudinal tracking groove defining relative motion of the pin. The tracking groove has a continuous cam side allowing unlimited travel of the pin along a complete fill or drain stroke. Opposite the continuous cam side is a discontinuous cam side defining traps for the pin should the user reverse directions before completing the fill or drain stroke. Two tracking grooves are preferably provided to define a complete allowed path along a fill tracking groove and a drain tracking groove. These two grooves converge near an end of the plunger adjacent a fluid content chamber of the syringe barrel.