Budesonide/formoterol is an effective treatment for both asthma and chronic obstructive pulmonary disease. This study compared the efficacy and safety of a novel hydrofluoroalkane (HFA) pressurised metered-dose inhaler (pMDI) formulation of budesonide/formoterol with that of budesonide pMDI and budesonide/formoterol dry-powder inhaler (DPI; Turbuhaler).This was a 12-week, multinational, randomised, double-blind, double-dummy study involving patients aged > or = 12 years with asthma. All patients had a forced expiratory volume in 1 s of 50-90% predicted normal and were inadequately controlled on inhaled corticosteroids (500-1600 microg/day) alone. Following a 2-week run-in, during which they received their usual medication, patients were randomised (two inhalations twice daily) to budesonide pMDI 200 microg, budesonide/formoterol DPI 160/4.5 microg or budesonide/formoterol pMDI 160/4.5 microg. The primary efficacy end-point was change from baseline in morning peak expiratory flow (PEF).In total, 680 patients were randomised, of whom 668 were included in the primary analysis. Therapeutically equivalent increases in morning PEF were observed with budesonide/formoterol pMDI (29.3 l/min) and budesonide/formoterol DPI (32.0 l/min) (95% confidence interval: -10.4 to 4.9; p = 0.48). The increase in morning PEF with budesonide/formoterol pMDI was significantly higher than with budesonide pMDI (+28.7 l/min; p < 0.001). Similar improvements with budesonide/formoterol pMDI vs. budesonide pMDI were seen for all secondary efficacy end-points. Both combination treatments were similarly well tolerated.Budesonide/formoterol, administered via the HFA pMDI or DPI, is an effective and well-tolerated treatment for adult and adolescent patients with asthma, with both devices being therapeutically equivalent.