The Genuair inhaler is a new multidose dry powder inhaler for the delivery of aclidinium bromide - a novel, long-acting, muscarinic antagonist in development for the treatment of chronic obstructive pulmonary disease (COPD). The primary aim of this study was to assess the inspiratory flow characteristics through Genuair in patients with moderate or severe COPD. Using a three-period cross-over design, 48 patients were randomised to inhale placebo powder through Genuair, HandiHaler A (slow, deep inhalation as per manufacturer's instructions) or HandiHaler B (fast, forceful inhalation). Three measurements of peak inspiratory flow (PIF), 10min apart, were recorded for each method of administration. The highest and average PIFs for the three attempts (mean+/-standard deviation) generated through the Genuair inhaler were 97.7+/-15.7 and 92.0+/-15.4L/min, respectively. Furthermore, 97% of inhalations with the Genuair inhaler were successful (activation of trigger threshold mechanism) and optimal (PIF> or =45L/min). The highest and average PIFs generated through HandiHaler A and B were significantly lower than with the Genuair inhaler. In conclusion, patients with moderate or severe COPD were able to generate sufficient inspiratory airflow through the Genuair inhaler to reliably inhale the full dose and reset the inhaler.