BACKGROUND Beclomethasone dipropionate (BDP) has been formulated as an extrafine aerosol (hydrofluoroalkane-134a [HFA]-BDP) [QVAR; 3M Pharmaceuticals; St Paul, MN], which gives improved lung deposition compared with chlorofluorocarbon (CFC)-BDP. The clinical efficacy of HFA-BDP has been established in adult asthma at a required dose below that of CFC-BDP, but has not been evaluated in children. OBJECTIVE To examine the efficacy and safety of HFA-BDP in childhood asthma. METHODS A 12-week, multicenter, randomized, double-blind, placebo-controlled, parallel-group study involving 353 children aged 5 to 12 years with moderate, symptomatic asthma. After a 2-week run-in period, patients were randomized to HFA-BDP, 80 micro g/d (n = 120); HFA-BDP, 160 micro g/d (n = 117); or HFA-placebo (n = 116) administered twice daily. METHODS Hospital outpatient. RESULTS HFA-BDP, 80 micro g/d and 160 micro g/d, produced a significant, dose-related increase from baseline in FEV(1) percent predicted compared with placebo. At week 12, mean changes from baseline in FEV(1) percent predicted were 9.2% (p < or = 0.01 vs placebo), 10% (p < or = 0.01 vs placebo), and 3.9% for the HFA-BDP 80 micro g/d, HFA-BDP 160 micro g/d, and placebo groups, respectively. There was also a significant decrease in daily beta-agonist use, improvement in peak expiratory flow, and increase [correction] in the percentage of days free from asthma symptoms (p < or = 0.05 for HFA-BDP, 160 micro g/d, vs placebo at weeks 11 to 12). HFA-BDP was well tolerated, with no significant differences in the incidence or nature of adverse events between HFA-BDP and placebo groups. Neither were there significant differences between groups in mean percentage change from baseline in the morning plasma cortisol level at week 12 or in the percentage of patients with morning plasma cortisol levels below the reference range at baseline and week 12. In a subgroup tested, the percentage of patients with an abnormal response to low-dose adrenocorticotropic hormone stimulation at week 12 was low and similar among all groups. CONCLUSIONS HFA-BDP, 80 to 160 micro g/d, is effective and safe in childhood asthma.