Abstract: An apparatus for dispensing a metered amount of aerosolized medication and/or for measuring breathing function includes a casing that defines a cavity, a first or discharge opening from which a subject inhales from the cavity or exhales into the cavity, a second or air opening through which air enters the cavity, and a third opening in fluid communication with the cavity between the first and second openings. The casing also defines an open pocket for receiving a pressurized canister and a fourth or medication opening through which the contents of the canister discharge into the cavity of the casing. A pressure transducer in fluid communication with the third opening senses the pressure of breath moving through the cavity. Alternatively, a fan and photocell assembly may replace the pressure transducer and sense the flow of gas through the cavity.