in the pharmacological treatment of asthma, the most suitable way is by inhalation, since this enables us to achieve a greater concentration of medicine in the affected organ than systemic medication, and besides the latter？s secondary effects are minimized. the suitable use of inhalers and hence their efficacy depends on very different factors. some of those of a merely technical kind are as follows: - a suitable volume of inhalation. - the rhythm of inhalation. - the length of the inspiratory apnea following administration of the medicine. - the coordination between the inspiration of the aerosol and activation of the device, in the case of the metered dose inhaler (mdi). one of the reasons for the incorrect use of mdi aerosols is the lack of coordination between activation of the device and inspiration. this has led to the design of different devices that avoid the need for this coordination, such as: inhalation chambers and devices for inhaling dry dust. it has also been suggested in the literature that the causes of these mistakes are to be found in the health professionals not knowing, or not suitably teaching the patients how to handle the devices. in spite of being designed to facilitate correct administration, suitable knowledge of the technique of their use by the patient is required.