The purpose of this study is to determine if a flexible dose of Symbicort has a similar effect on the airways of patients with asthma as a higher fixed-dose of Symbicort with additional glucocorticosteroids added.

Inclusion Criteria:

• Diagnosis of asthma for at least 6 months
• Prescribed daily use of glucocorticosteroids for at least 3 months prior to visit one

Exclusion Criteria:

• Respiratory infection affecting asthma within 30 days prior to study
• Intake of oral, rectal, or parenteral glucocorticosteroids within 30 days prior to study
• Any significant disease or disorder that may jeopardize the safety of the patient