A dry powder inhaler comprises an airway (1) along which, in use, air is drawn from an upstream, inlet end (2) to a downstream, outlet end (3). The airway (1) includes a medicament presentation region (4) at which, in use, a dose of medicament is presented to the airway (1), a primary air inlet (10), and a barrel (5) extending from the medicament presentation region (4) to the outlet end (3) of the airway (1). The inlet end of the barrel (5) is of reduced internal dimension relative to the medicament presentation region (4) and relative to the outlet end of the barrel (5), such that the inlet end of the barrel (5) constitutes a constriction of the airway (1). At least one secondary air inlet (11) is disposed such that, in use, air enters the airway (1) from the secondary air inlet (11) in a direction that is substantially orthogonal to the direction of flow of air along said barrel (5).