A dry powder inhaler, comprising: an inlet channel (204, 405, 602, 704, 803a, 803b, 903a) for air (203, 411) to enter the inhaler (400, 500, 700); a single actuator (201, 409, 1006); a chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c) to receive air from the inlet channel (204, 405, 602, 704, 803a, 803b, 903a), the chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c) being of a size and shape to contain the single actuator (201, 409, 1006), and the chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c) having an axis, wherein the geometry of the inhaler (400, 500, 700) is such that a flow profile is generated within the chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c) that causes the single actuator (201, 409, 1006) to oscillate generally along the axis in response to air flow; a retaining member (205, 408, 1005) disposed at an end of the chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c) opposite the inlet channel (204, 405, 602, 704, 803a, 803b, 903a), the retaining member (205, 408, 1005) having one or more openings sized to permit air and a powdered medicament to pass through the retaining member (205, 408, 1005), and to prevent the actuator (201, 409, 1006) from passing through the retaining member (205, 408, 1005); and an outlet channel (402, 502, 702, 804, 805a, 805b, 904, 1401) as an exit for air and the powdered medicament; wherein the diameter of the chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c) is at least 1.5 times the diameter of the inlet channel (204, 405, 602, 704, 803a, 803b, 903a) at an entrance to the chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c) and the cross-sectional area of the flow path through the inhaler undergoes a step increase at the entrance to the chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c), wherein the actuator (201, 409, 1006) is large enough that it cannot pass through the inlet channel (204, 405, 602, 704, 803a, 803b, 903a) and cannot pass through the openings in the retaining member (205, 408, 1005) and wherein a ratio of the diameter of the chamber to the diameter of the single actuator (201, 409, 1006) within the chamber is between 1.0 and 2.0; characterized in that the single actuator (201, 409, 1006) is rotatable in up to three dimensions within the chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c) and is a bead to which the powdered medicament is adhered, the oscillation of the single actuator (201, 409, 1006) thus detaching the powdered medicament from the surface of the actuator (201, 409, 1006) to be entrained by the air and delivered to the patient through the outlet channel (402, 502, 702, 804, 805a, 805b, 904, 1401). an inlet channel (204, 405, 602, 704, 803a, 803b, 903a) for air (203, 411) to enter the inhaler (400, 500, 700); a single actuator (201, 409, 1006); a chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c) to receive air from the inlet channel (204, 405, 602, 704, 803a, 803b, 903a), the chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c) being of a size and shape to contain the single actuator (201, 409, 1006), and the chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c) having an axis, wherein the geometry of the inhaler (400, 500, 700) is such that a flow profile is generated within the chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c) that causes the single actuator (201, 409, 1006) to oscillate generally along the axis in response to air flow; a retaining member (205, 408, 1005) disposed at an end of the chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c) opposite the inlet channel (204, 405, 602, 704, 803a, 803b, 903a), the retaining member (205, 408, 1005) having one or more openings sized to permit air and a powdered medicament to pass through the retaining member (205, 408, 1005), and to prevent the actuator (201, 409, 1006) from passing through the retaining member (205, 408, 1005); and an outlet channel (402, 502, 702, 804, 805a, 805b, 904, 1401) as an exit for air and the powdered medicament; wherein the diameter of the chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c) is at least 1.5 times the diameter of the inlet channel (204, 405, 602, 704, 803a, 803b, 903a) at an entrance to the chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c) and the cross-sectional area of the flow path through the inhaler undergoes a step increase at the entrance to the chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c), wherein the actuator (201, 409, 1006) is large enough that it cannot pass through the inlet channel (204, 405, 602, 704, 803a, 803b, 903a) and cannot pass through the openings in the retaining member (205, 408, 1005) and wherein a ratio of the diameter of the chamber to the diameter of the single actuator (201, 409, 1006) within the chamber is between 1.0 and 2.0; characterized in that the single actuator (201, 409, 1006) is rotatable in up to three dimensions within the chamber (202, 406, 506, 802a, 802b, 902a, 902b, 902c) and is a bead to which the powdered medicament is adhered, the oscillation of the single actuator (201, 409, 1006) thus detaching the powdered medicament from the surface of the actuator (201, 409, 1006) to be entrained by the air and delivered to the patient through the outlet channel (402, 502, 702, 804, 805a, 805b, 904, 1401).