Ciclesonide is a novel, lung-activated, inhaled corticosteroid with once-daily efficacy and potent anti-inflammatory activity. The aim of the study was to compare the effect of ciclesonide and fluticasone propionate on exhaled nitric oxide (FENO), pulmonary function, and other parameters used in clinical evaluation of patients with mild allergic asthma. The study indicates that ciclesonide (in a daily dose of either 80 or 160 microg) induces both a faster and stronger decrease of FENO in comparison with fluticasone (100 microg twice daily). In both groups of patients treated with ciclesonide, the highest decrease in FENO levels was observed after 2 weeks of treatment. In the group of patients treated with fluticasone, this maximum effect was not observed till 8 weeks. An improvement in spirometric indices was observed in all groups studied. Statistical differences between the groups were not found; however, there was a trend toward higher increase in the group receiving 160 microg of ciclesonide. In all groups studied we observed clinical improvement (asthmatic symptoms and consumption of rescue medication were reduced), but there were no significant differences between these groups. Our results indicate that ciclesonide, compared with fluticasone, has stronger anti-inflammatory activity in patients with mild allergic asthma.