A dry powder inhaler comprises a main airflow path including a cyclone chamber (134) having an air inlet and being so shaped that at least a part of the chamber (134) decreases in cross-sectional area in a direction away from the air inlet, so as thereby in use to set up a reverse flow cyclone in the chamber (134). A bypass airflow path bypasses the cyclone chamber (134) and the main and bypass airflow paths communicate with a mouthpiece (128). The cyclone chamber (134) may be provided by a part (122) which is removable from the rest of the inhaler for regular replacement thereof.
