Abstract: A hypodermic syringe made up of a retractable needle assembly, a barrel, and a plunger. The needle assembly and the barrel are attached in such a way that they may be separated and the plunger and the needle assembly are adapted to be secured together. When the plunger is pushed all the way forward, the plunger and the needle assembly become secured to each other. When the plunger is pulled back, the needle is retracted. The needle assembly or the plunger and the barrel each have interlocking securing mechanisms to affix the needle assembly near the proximal end of the barrel. The mechanisms prevent the removal of the retracted needle assembly from the barrel. Thus, the syringe is not reusable and provides protection against accidental needlesticks. The syringe may have a compressible rubber collar around the tip of the plunger to provide for selective engagement of the plunger to the needle assembly and to expel all the fluid contents of the syringe.