Efficacy and Safety of Roflumilast Taken in the Morning or Evening in Patients With Stable Asthma (12 to 70 y) (BY217/M2-015)

Main Inclusion Criteria: * Written informed consent * Diagnosis of persistent bronchial asthma (with reference to the Global Initiative for Asthma Guidelines 2002) * Baseline FEV1 50 - 85% in patients either untreated or receiving e.g. short-acting bronchodilators, DSCG, nedocromil, anticholinergics, long-acting bronchodilators, theophylline/aminophylline, lipoxygenase inhibitors, leukotriene antagonists, alone or in combination * Baseline FEV1 60 - 90% in patients receiving not more than 500 mcg BDP-CFC (or equivalent) and/or in combination with any other asthma medication mentioned above * No change in the asthma treatment 4 weeks prior to baseline period * Patients who, with the exception of asthma, are in good health Main Exclusion Criteria: * Poorly controlled asthma: requirement of a course of oral and/or parenteral glucocorticosteroids 4 weeks prior to the baseline, or admission to hospital for asthma (including treatment in an emergency room) 4 weeks prior to the baseline period, or asthma exacerbation in the last 4 weeks prior to baseline period * Patient using regularly \>8 puffs/day rescue medication prior to baseline * History of lower airway infection in the last 4 weeks prior to baseline period * Diagnosis of chronic obstructive pulmonary disease and/or other relevant lung diseases * Heavy smoker: currently: \>20 cigarettes/day and/or \>10 pack years, ex-smoker: with a smoking history of ≥10 pack years * Clinically relevant abnormal laboratory values suggesting an unknown disease and requiring further clinical evaluation * Liver insufficiency (Child Pugh A or worse) * Active hepatitis * Known infection with HIV * Diagnosis or history of cancer (other than basal cell carcinoma) or recurrence within 5 years prior to study start * Alcohol and/or drug abuse * Suspected hypersensitivity and/or contraindication to any ingredients of the study medication (roflumilast) or rescue medication * Pregnancy or patient of childbearing potential who is not using reliable method of contraception * Patients not able to follow study procedures, e.g. due to language problems, psychological disorders * Suspected inability or unwillingness to comply with the study procedures