Abstract: This invention relates to a device for controlling the delivery of therapeutic respiratory agents to the respiratory system of a patient. The device includes a drug delivery means which is extremely controlled by a fluid flow control means in response to the respiratory cycle of the patient. The device is so arranged that, upon inhalation, a therapeutic agent is delivered by the device of the invention to an individual in a programmable manner so that the quantity and periodicity of the therapeutic agent can be varied according to a user's requirements.