[en] Asthmatic patients often use inhalers to deliver medication to their lungs, and many current inhalers contain chlorofluorocarbons (CFCs) as propellant. Due to the damage that CFCs pose to the earth's ozone layer, these inhalers will soon be replaced by alternative methods. One possibility is that drugs in the form of dry powder could be administered by oral inhalation. Numerous studies have been performed on the deposition of aerosol particles in upper respiratory tract casts of humans. These studies and several others have been summarized by Yu, C.P. et al. Although mathematical models exist for the tracheobronchial (TB) and pulmonary regions of the lungs, the complex anatomy of the oral, oropharyngeal and laryngeal (OPL) region makes it difficult to model the depositions in the complete respiratory tract. The present study provides experimental data on the fractional deposition of monodisperse aerosol particles (ranging from 3 to 22 μm) in the OPL and TB regions using silicone rubber (open-quotes silasticclose quotes) casts at a constant 30 L/min flow rate through the mouth. The purpose was to determine the deposition open-quotes hot spotsclose quotes of micrometer size dry powders in different regions of the respiratory tract after a moderate oral puff