Abstract: A disposable syringe for use in a needleless hypodermic injector includes a transparent, plastic barrel with an injection orifice in a closed front end thereof and an open rear end for receiving a plunger. The barrel is filled with medicine using a needle, which may be integral with the barrel, by partially withdrawing the plunger from the barrel to suck medicine through the injection orifice. The barrel and plunger are placed in an injector and the injector is actuated to push the plunger into the barrel, discharging the medicine. Alternatively, the syringe is filled with medicine while in an injector of the type which includes a removable injection head and a removable charging or filling head.