Abstract: A disposable hypodermic syringe comprises an outer barrel, an inner barrel slidingly disposable in the outer barrel, a hypodermic needle disposed axially at the front end of the outer barrel so as penetrate its front end wall and being held, at its rear end, by the front end wall of the inner barrel, and a plunger which is slidingly disposable in the inner barrel. The outer barrel includes elements for interlocking with the inner barrel when the inner barrel is in a fully inserted position. The plunger includes release elements for releasing the inner barrel from the outer barrel while interlocking with the inner barrel so as to allow the inner barrel and the plunger to be withdrawn in combination with the hypodermic needle for a distance sufficient to displace the needle into a space formed between the outer barrel and the inner barrel.