The aim of the study is to compare the safety and efficacy of ciclesonide versus fluticasone propionate on the lung function, symptoms, use of rescue medication, and occurrence of side effects (such as candidiasis, hoarseness) in adults with persistent asthma. Ciclesonide will be inhaled twice daily at one dose level; fluticasone propionate will be inhaled twice daily at one dose level. The study duration consists of a baseline period (2 weeks) and a treatment period (24 weeks). The study will provide further data on safety and tolerability of ciclesonide.