Dry powder inhalers (DPIs) have been available for delivering drugs to the lungs for over 30 years. In the last decade there has been a big increase in DPI development, resulting partly from recognised limitations in other types of inhaler device. Many companies are developing DPIs for asthma and chronic obstructive pulmonary disease (COPD) therapy, and there is increasing recognition of the potential role of DPI systems for other therapies, such as inhaled antibiotics and peptides/proteins. Optimised drug delivery may be achieved not only by improvements to devices, but also via more sophisticated formulations that disperse easily in the inhaled air-stream and which may often be delivered by relatively simple inhaler devices. DPIs could become the device category of choice for a wide range of inhaled therapies, involving both local and systemic drug delivery.