Developing more effective and convenient inhalation devices for the treatment of obstructive pulmonary diseases is at least as important as designing new drugs. In recent years, existing inhalation systems have undergone many technical modifications and there have also been many new developments. All of these systems have their own particular attributes and characteristics. Two fundamentally different modes of operation are represented by propellant-driven metered-dose inhalers (pMDI) on the one hand and dry powder inhalers (DPI) on the other. However, none of the systems developed so far can be considered ideal. The Respimat Soft Inhaler (Respimat SI) was developed in the light of experience with previous systems and was launched in Germany at the beginning of 2004. The aim in developing this new type of inhaler was to avoid the well-known drawbacks typically associated with pMDI and DPI. The Respimat SI requires neither a chemical propellant nor batteries. The active ingredients are dissolved in water and the solution is atomised using mechanical energy only imparted by a spring which, when released, provides the power to force the solution through an extremely fine nozzle system. Two fine jets of liquid are produced. They converge at an optimised angle and the resulting impact generates a fine mist which is slow-moving and lasts for about 1.5 seconds; moreover, a high proportion of the droplets fall into the fine particle fraction. All of these features allow excellent lung deposition and reduced oropharyngeal deposition. Coordination between actuation and inhalation is less critical as compared with pMDI due to the fact that the mist is both slow-moving and long-lasting. A further advantage is that the mist is generated independently of the patient's inspiratory flow. The Respimat SI meets the requirements for an ideal inhaler better than any other previous device and must therefore be regarded as a significant new development.