Inclusion Criteria:

• Minimum of 3 months history of asthma, diagnosed according to the American Thoracic Society (ATS) definition (9).
• Prescribed inhaled GCS at a dose of 400μg/day of budesonide (or equivalents)and within the approved label for the relevant drug during the last 3 months prior to Visit 1.
• Either daily maintenance treatment with both inhaled GCS and long-acting b2-agonist(LABA) or daily treatment with inhaled GCS alone (i.e. without LABA)
• A history of suboptimal asthma control the month prior to enrolment as judged by the investigator
• Use of ≥3 inhalations of as needed medication for symptom relief during the last 7 days before enrolment

Exclusion Criteria:

• Previous treatment with Symbicort Single Inhaler;
• Use of any b-blocking agent, including eye-drops and oral GCS as maintenance treatment.
• Known or suspected hypersensitivity to study therapy or excipients.
• A history of smoking ≥ 10 pack years.
• Asthma exacerbation requiring change in asthma treatment during the last 14 days prior to or at Visit 1.