A new hydrofluoroalkane-beclomethasone dipropionate (HFA-BDP) aerosol markedly increases drug delivery to the airways. Therefore, even low doses of HFA-BDP should be effective, and the present study assesses this. A randomised, double-blind, crossover study was used to compare the effect of placebo, HFA-BDP 50 microg or 100 microg given q.d. (QVAR(TM) Autohaler(TM); 3M Pharmaceuticals, St. Paul, MN, USA) on exercise-induced bronchoconstriction and exhaled nitric oxide (eNO). After a 14-day run-in, 25 children (5-14 yrs old) entered three 4-week treatment periods, separated by a 1-week washout. After each period, the fall in forced expiratory volume in one second (FEV1), after an exercise test, and eNO were measured. Significant treatment effects with no carry-over or period effects were seen for both eNO and maximum fall in FEV1 after exercise. Differences were seen between placebo (fall in FEV1=27.9%; eNO=14.4 parts per billion (ppb)) and either dose of HFA-BDP, but not between the two active doses (50 microg: fall in FEV1=20.8%, eNO=9.3 ppb; 100 microg: fall in FEV1=20.9%, eNO=8.9 ppb). In conclusion, low q.d. doses of hydrofluoroalkane-beclomethasone dipropionate reduced exhaled nitric oxide and exercise-induced bronchoconstriction. Further studies are needed to assess whether q.d. administration of beclomethasone dipropionate is as effective as b.i.d. administration.