In clinical practice, pressurised metered-dose inhalers (pMDIs) used with or without a spacer device, dry powder inhalers (DPIs), and nebulisers are used for aerosol delivery. In a 2005 systematic review, the authors concluded that these aerosol drug delivery devices were equally efficacious provided that they were used appropriately.4 In most, but not all the trials reviewed, the investigators tested single dose strengths of β agonists in different devices. These doses were often designed to approximate the plateau of the dose-response curve, thereby limiting the ability to differentiate between devices. Only a few of these studies compared the bronchodilator responses to a range of β-agonist doses. Since publication of that systematic review, several new devices have been marketed for clinical use and new clinical uses for inhaled therapies have emerged. Comparative trials now tend to be designed as cumulative dose-response studies or single doses over a therapeutic range.5