Local administration of drugs by means of aerosol device is widely used in the treatment of asthma. Nevertheless, the effectiveness of this method depends on an adequate inhalation technique (IT), which available evidence has shown to be rather problematic. The aim of this study was to assess IT in out-patients with bronchial asthma who frequently use aerosol therapy with Pressurized Metered dose inhalers (MDI), pressurized inhalers with spacer (MDI-S) and the Astra-Draco Turbuhaler system (TH). A sample of 150 adults with asthma were evaluated. These patients had been followed up for than two years and they often used one of the devices mentioned above. The IT has broken down into several steps for each procedure. Percentages of patients with one error in the IT were 50%, 44% and 42% for MDI, MDI-S and TH procedures, respectively. 18%, 20% and 14% of patients committed three errors in the IT, respectively. Differences detected were not significant. Seven patients committed errors in every step of the IT. In conclusion, the level of errors found in our study is high, similar to that cited in the existing literature. It is also roughly equivalent for the three devices tested. We believe that the proper teaching monitoring of IT skills is highly important in the treatment of bronchial asthma.