A Blinded Study To Examine The Ability Of PF-610,355 To Open The Airways In Asthmatic Patients.

Inclusion Criteria: * Reversible asthmatic patients (\>15% increase in FEV1 following 200ug salbutamol). * FEV1 greater than or equal to 60% predicted * Stable disease for at least the previous 3 months Exclusion Criteria: * Subjects requiring rescue medication on greater than 2 occasions in the 72 hours prior to screening * Subjects with a history of pulmonary disease other than asthma.