A breath powered dry powder inhaler configured to deliver particles to the pulmonary circulation of a subject comprises a chamber for containing the particles and a mouthpiece. Portions of the inhaler define a flow path leading from at least one inlet (119) to said chamber through said chamber and through at least one outlet (127) from said chamber to the mouthpiece. The at least one inlet and the at least one outlet are further configured so that air from the at least one inlet is directed across said at least one outlet and controls exit from the chamber of powder entrained within the flow. In embodiments the at least one inlet (119), the at least one outlet (127) and the chamber are configured so that in use air entering the chamber circulates within the chamber for promoting entrainment and lifting of a powder in the chamber. In these embodiments the inlet may define a first direction for air entry into the chamber, the outlet may define a second direction generally perpendicular to the first direction for air and powder leaving the chamber, and the inlet (119), outlet (127) and chamber may be configured so that in use air within the chamber circulates about an axis directed generally perpendicular to the first and generally perpendicular to the second direction. The chamber may contain a cohesive powder e.g. a diketopiperazine, and the powder may contain insulin or another medicament.
