A special new device for diagnostic (bronchoprovocation) and therapeutic aerosol application is described. It consists of a high quality nebulizer system combined with a 10-liter storage bag which serves as an aerosol 'conditioner' (saturated ambient temperature and pressure conditions) and as a holding chamber to increase the respirable aerosol fraction and hence pulmonary deposition (Pari Provocation Test I). It allows ten times better standardized pulmonary aerosol deposition compared with the generally used nebulizers for calculation of dose-response curves especially for asthma provocation and dilatation tests. If slow inspiratory vital capacity maneuvers are used, pulmonary deposition of about 100 mg aerosol is achieved in children and adults. This device is especially important when exact dosing (also for therapeutic reasons) is required in the expanding field of topical and systemic aerosol application to or via the lung.