Background: The efficacy of long-acting β-agonists (LABAs) in asthma has been demonstrated but their safety remains an issue, particularly in children. Co-therapy with inhaled corticosteroids (ICs) is recommended in persistent asthma. However, drug-use studies suggest frequently inadequate IC adherence, possibly explaining the occurrence of exacerbations. There is a need for detailed analyses of patterns of use of LABAs and ICs to describe asthma outcomes related to LABAs in monotherapy and at different levels of concomitant ICs, to explore the role of adherence in LABA safety, and to identify populations possibly at risk of adverse LABA-related asthma outcomes.Methods: Summarise available evidence on the risks of LABAs in asthma; develop questionnaires and instruments for the study; identify, in the UK and France, paediatric (6-15) and adult (16-40) patients with persistent asthma treated by LABAs; and link distinct datasets for this group using past and ongoing prescriptions provided by GPs and identified from electronic health records, dispensed therapy identified from claims data, information collected from prescribers, and details on exposures and outcomes collected by computer-assisted telephone interviews with patients over a prospective 24-month period. Analyze the linked datasets to characterise individual asthma care in detail and with high validity, describe patterns of use of LABAs and ICs, and relate these patterns to asthma outcomes. Disseminate results to the scientific community, patients’ associations, physician’s associations, and regulators.Deliverables: Ranking of observed patterns of LABA and IC use according to risk of adverse outcomes due to LABAs. Identification from prescriber and patient data of predictors of patterns of use which put patients at risk. Results for regulators to use regarding recommendations to prescribers and patients on the use of LABAs. Assessment of the potential impact of these recommendations on public health.