This trial was performed in a randomized double-blind manner on four different days in 13 asthmatic patients in order to compare the bronchodilator efficacy of two different inhalation devices, Inspirease (IP) and Aerochamber (AC), to the conventional metered dose inhaler (MDI). The results showed that clenbuterol determined a significant FEV1 increase inhaled either via MDI or via IP and AC. IP caused a greater bronchodilatation than AC, 30 min after clenbuterol administration. IP caused a greater mean increase (P less than 0.05) in FEV1 than the MDI at all time intervals; AC provided an improvement in bronchodilator response over directly administered MDI. Such responses are only marginally clinically relevant when patients use MDI correctly. These devices are mainly indicated in patients with poor hand-lung coordination.