OBJECTIVE:To evaluate the efficacy and tolerability of a novel hydrofluoroalkane (HFA) pressurised metered dose inhaler (pMDI) formulation of budesonide (Pulmicort) versus the conventional chlorofluorocarbon (CFC) pMDI formulation in paediatric patients with asthma. METHODS:This was a Phase III, multicentre, 12-week, double-blind, randomised, parallel-group study involving children (6-12 years of age) with mild to moderate asthma. Patients received either budesonide HFA pMDI or budesonide CFC pMDI 200 mug twice daily, with or without a spacer (NebuChamber/Nebunette). Primary efficacy endpoint: mean percentage change in forced expiratory volume in 1 second (FEV(1)) from baseline to week 12. Secondary efficacy endpoints included changes in FEV(1) per cent of predicted normal, forced vital capacity, morning and evening peak expiratory flow rate, asthma symptoms and use of rescue medication. RESULTS:A total of 159 patients received treatment (HFA 77, CFC 82). For mean percentage change in FEV(1) from baseline to week 12, the difference between the treatments (CFC pMDI - HFA pMDI) was -3.1% (95% confidence interval [CI] -8.0% to 1.8%) for the full analysis set and was not affected by spacer use. The upper CI was < 10% (the predefined non-inferiority margin), so non-inferiority was demonstrated. Improvements in the secondary efficacy endpoints with both budesonide formulations were not significantly different. In both groups there were similar numbers of adverse events and no evidence of oral candidiasis at week 12. CONCLUSIONS:Treatment with budesonide HFA pMDI is effective and well tolerated in children with asthma and is clinically comparable to budesonide CFC pMDI.