Hydrofluoroalkane-134a beclomethasone dipropionate (HFA-BDP) extra-fine aerosol and HFA-fluticasone propionate (HFA-FP) are chlorofluorocarbon-free inhalers. We conducted an 8-week, open study to demonstrate the equivalence of HFA-BDP (800 microg day(-1)) and HFA-FP (1000 microg day(-1)) in moderate to severe asthma. Symptomatic patients on 500-1000 microg day(-1) CFC-BDP (or equivalent) and short-acting beta-agonist, were randomized to HFA-BDP (n = 101) or HFA-FP (n = 97) after 7-14 (+/-2) day run-in. In the intent-to-treat (ITT) population (n = 198), both treatments provided clinically and statistically significant improvements in asthma control, with increases in peak expiratory flow in the morning (AM PEF) and asthma symptoms (within treatment analysis P<0.05). Mean (SE) change in AM PEF from baseline at week 8 was equivalent (defined as 90% CI for the mean difference between treatments within +/-25 l min(-1)) in the two groups: 29.59 (5.19) l min(-1) for HFA-BDP vs. 17.3 (5.45) l min(-1) for HFA-FP (90% CI-0.02, 24.91). For the perprotocol population (n = 121), the mean (SE) change in AM PEF from baseline was not equivalent; AM PEF improved to a significantly greater extent in the HFA-BDP group than HFA-FP group [34.84 (7.08) vs. 20.63 (7.32) l min(-1) P<0.01; 90% CI; 2.66, 31.10]. At week 8 in the ITT population, there were no statistically significant differences in FEV1, beta-agonist use, asthma symptom/sleep disturbance scores, or percentage of days without asthma symptoms/sleep disturbance. There was a significantly greater reduction from baseline in mean eosinophil count for HFA-BDP compared with HFA-FP at weeks 3 and 8 (P<0.01), and eosinophil cationic protein value at week 8 (P<0.01). Both treatments were well tolerated and there were no statistically significant differences in urinary cortisol creatinine parameters. In conclusion, this study showed that, in patients with moderate-to-severe symptomatic asthma, HFA-BDP extra-fine aerosol 800 microg(-1) was at least as effective and equally well tolerated as 1000 microg day(-1) HFA-FP.