A dry powder inhaler (100) comprises a chamber (150) for containing a powder and a housing (120) in which the chamber (150) is mounted. The housing (120) defines first (118,124) and second flow paths (140) leading from outside the inhaler (100) to a mouthpiece (130), the first flow path (118,124) allowing air to flow through the chamber (150) and the second flow path (140) allowing air to bypass the chamber. The first (118,124) and second (140) paths are configured so that in use airflow bypassing the chamber (150) is directed to impinge upon airflow exiting the chamber (150) for deagglomerating powder particles as they exit the chamber (150). The chamber (150) may contain a cohesive powder e.g. a diketopiperazine, and the powder may contain insulin or another medicament.
