A dry powder inhaler incorporates a cyclone chamber (4) comprising at least one air inlet (6) and an outlet (10) wherein the configuration of the air inlet (6) and the shape of the chamber (4) is such that in use a reverse flow cyclone is set up in the chamber (4). The chamber (4) further comprises flow disrupter means, e.g. the upper surface (14) of a protrusion (12) from the base, disposed so as in use to restrict air flowing from the base of the chamber (4) in an axial direction.