Comparison of the Efficacy/Safety of Symbicort® Turbuhaler®,Seretide™ Diskus™ 50/500 µg & Terbutaline Turbuhaler® 0.4 mg

Inclusion Criteria: * Diagnosed with asthma since at least 6 months prior to first visit * Prescribed daily use of glucocorticosteroids for at least 3 months prior to first visit * At least one asthma exacerbation more than one but less than twelve months prior to first visit Exclusion Criteria: * Respiratory infection affecting asthma within 30 days before first visit * Use of oral, rectal, or parenteral glucocorticosteroids for within 30 days before first visit * Any significant disease or disorder that may jeopardize the safety of the patient Additional inclusion and exclusion criteria will be evaluated by the Investigator.