Abstract: A tubular expansion chamber with ends each having apertures for inlet and outlet, respectively, for use with a conventional metered-dose inhaler for delivering medicament to a user suffering from asthma or other similar respiratory ailment. The expansion chamber with a metered-dose inhaler inserted in the inlet aperture intercepts the high-velocity discharge of medicament from a pressurized inhaler and produces a concentrated mist for withdrawal by inhalation by the user through the outlet aperture. The expansion chamber is closed on its outlet end by a removable end cap with mouthpiece surrounding and defining the outlet aperture. The constant volume expansion chamber is dimensionally optimized to maximize medicament concentration in a mist of small particles, able to be substantially withdrawn by a asthmatic user in a short, quick breath characteristic of persons with respiratory ailments such as asthma or chronic bronchitis.