This double-blind, stratified, parallel group study is to determine whether aiming for 'Total control' results in better airway hyper-responsiveness than maintaining the treatment level at which 'Well-controlled' asthma was achieved. The primary endpoint is the mean change in PC20 methacholine. Well controlled subjects (as assessed after a 12 week run-in period) will enter a 24 week treatment period during which they will record PEF(Peak Expiratory Flow), symptoms, rescue beta2-agonist use over 24 hours, night time awakenings, asthma exacerbations, emergency visits due to asthma and Adverse Events.

At every visit lung function measurements and airway hyper-responsiveness will be measured.

A multi-centre, randomised, double blind, stratified, and parallel group study to evaluate whether a treatment strategy based on aiming for 'Total control' results in better airway hyper-responsiveness than a treatment strategy based on maintaining the treatment level at which 'Well-controlled' asthma was achieved.

Inclusion criteria:

• History of asthma of at least 6 months.
• Subjects who have received fluticasone propionate at a dose of 100 mcg bd to 250 mcg bd or equivalent with or without a long acting beta2-agonist for at least 4 weeks before the start of the run-in period, at a constant dose.
• Subjects who are able to understand and complete an electronic diary card.

Exclusion criteria:

• Subjects who have been hospitalized for their asthma within 4 weeks of study entry.
• Subjects who had an acute upper respiratory tract infection within 4 weeks or a lower respiratory tract infection within 4 weeks prior to study entry.
• Subjects who received oral, parental or depot corticosteroids within 4 weeks prior to study entry.
• Subjects who have a known respiratory disorder other than asthma and/or systemic/thoracic abnormalities which influence normal lung function.
• Subjects who have more than 5 pack years.
• Subjects who currently smoke.