The efficacy and systemic effects of ciclesonide, a novel glucocorticosteroid, inhaled via pressurized metered-dose inhaler (pMDI) were compared with fluticasone propionate pMDI in 26 patients with asthma, using a randomized, double blind, placebo-controlled, double dummy, 6-period crossover study design. Treatments were placebo, ciclesonide 320 microg (ex-actuator dose) once daily (o.d.), ciclesonide 640 microg o.d., ciclesonide 640 microg twice daily (b.i.d.), fluticasone propionate 440 microg (ex-actuator dose) b.i.d., and fluticasone propionate 880 microg b.i.d. The primary variable was area under the plasma cortisol concentration-time curve over 24 h (plasma cortisol AUC(0-24), relative to placebo) derived from samples taken every 2 h, on the 9th day of treatment. Secondary variables were 24-h urinary cortisol excretion and PC20 for adenosine 5'-monophosphate (AMP) (relative to placebo and expressed in doubling concentrations). Ciclesonide did not affect 24-h cortisol secretion. Fluticasone propionate suppressed cortisol secretion as demonstrated by a decrease in plasma cortisol AUC(0-24), relative to placebo, by 29% (95% CI 15-41) and 59% (95% CI 51-66) with 440 and 880 microg b.i.d., respectively. PC20 more than doubled with each active treatment, but no statistically significant dose-response effect could be established. It was concluded that moderate to high doses of fluticasone propionate suppressed cortisol secretion, that ciclesonide did not suppress cortisol secretion, and that all active treatments decreased hyperresponsiveness to AMP.