Abstract: The present invention constitutes a portable nebulizer capable of producing a finely divided aerosol having uniformly sized droplets. The nebulizer includes a source of fluid such as a capillary tube coupled to a fluid reservoir to which a high voltage is applied in order to generate the aerosol by electrical atomization. The nebulizer further includes a piezoelectric crystal and a mechanism for deforming the crystal so as to generate the required voltage. The nebulizer further includes a means for mechanical positive displacement fluid control for controlling the amount of fluid atomized. By using electrical atomization to generate the aerosol and by piezoelectrically generating the voltage required for atomization, a nebulizer is provided which may be of small size so as to be suitable for hand-held operations, yet is capable of producing measured amounts of finely divided aerosols which are substantially monodispersed.