The purpose of this study is to confirm the dose of roflumilast to be used for asthma management by comparing the effects of 250 mcg and 500 mcg oral roflumilast with placebo on pulmonary function and asthma symptoms.

Main Inclusion Criteria:

• Diagnosis of persistent chronic bronchial asthma
• Baseline lung function within specified parameters
• No change in asthma treatment during the last 4 weeks prior to start of baseline period
• Stable clinical state
• Except for asthma, in good health
• Non-smokers or ex-smokers

Main Exclusion Criteria:

• Poorly controlled asthma
• Diagnosis of chronic pulmonary disease and/or other relevant lung diseases
• Patients using continuously (more than 3 days per week) > 8 puffs/day rescue medication