Abstract: An interchangeable needle assemblage for a hypodermic syringe which enables needles of varying lengths and characteristics to be readily attached to the barrel of an existing syringe or vial. Where double-ended needles are utilized, the barrel or vial has an opening with a sealing membrane disposed thereacross, adapted to be pierced by the inner end of the needle. Carried on the barrel is a locking type ferrule having a pair of internal locking shoulders located on opposite sides of a slot. A needle hub assembly is receivable in the slot, being rigidly affixed to the needle at a point intermediate the ends thereof, said assembly having finger-engageable ears to facilitate grasping of the hub, and further having shoulders cooperable with the locking shoulders on the ferrule. To install a needle on the syringe or vial, the hub is first inserted into the ferrule so that the hub shoulders by-pass the internal locking shoulders of the ferrule.