Abstract: A disposable needleless injection device includes an integral unit that is dimensioned and arranged to be grasped in the hand of a user. The system is spring-loaded and is manufactured and shipped with the spring in a pre-cocked condition. An integral ampule is fillable by manipulation of a thrust rod/shaft which extends longitudinally through the device and is able to be grasped by a user. Once the unit is filled with a selected medication, it is held proximate the skin in order to inject the selected dosage. The unit is constructed from a maximum of eight component parts and is assembled in a matter of moments by unskilled personnel.