A dilution spacer for a metered-dose inhaler comprises an enclosure defining a dilution chamber. An ambient air inlet and an outlet are in fluid communication with the dilution chamber. The ambient air inlet is positioned opposite the outlet whereby suction through the outlet from outside the enclosure draws ambient air into the enclosure through the ambient air inlet to generate an airflow path from the ambient air inlet through the dilution chamber and out of the outlet. The dilution spacer may include an actuator inlet configured to securely releasably interengage a metered-dose inhaler actuator mouthpiece, or may include a receptacle having an actuator nozzle and configured to receive a metered-dose inhaler canister, A metered-dose inhaler plume entering the dilution chamber intersects the airflow path thereto and airflow along the airflow path entrains and redirects at least a portion of the metered-dose inhaler plume toward the outlet.
