A disposable injector with a cylinder/piston unit that can be filled at least temporarily with active substance, with a housing in which a pretensioned and releasable mechanical spring energy reservoir is arranged, and with at least one piston-actuating ram positioned between the spring energy reservoir and the piston of the cylinder/piston unit. The piston-actuating ram has two draw hooks that engage around the housing in some areas. In addition, the piston-actuating ram is separable from the housing by means of the relaxing spring energy reservoir. With the present invention, a disposable injector is developed which, with a small overall size, comprises only a small number of components and, while being easy to handle, ensures safe storage and operation
