Background: Asthma exacerbations affect the quality of life of patients with asthma and have a major effect on the overall costs of asthma care. An asthma self-management plan that advises the temporary quadrupling of inhaled corticosteroid dose may prevent asthma exacerbations, but this needs to be confirmed before being adopted widely., Objectives: To compare the clinical effectiveness and cost-effectiveness of an asthma self-management plan that advises patients to temporarily quadruple the dose of inhaled corticosteroid when asthma control starts to deteriorate with a standard self-management plan., Design: A multicentre, parallel-group, pragmatic randomised trial, with follow-up for 12 months., Setting: Primary and secondary care across 207 sites in the UK., Participants: Asthma patients aged ≥ 16 years treated with an inhaled corticosteroid who had experienced at least one exacerbation in the previous 12 months., Interventions: Participants were randomised (1 : 1) to a usual-care self-management plan or to a modified self-management plan that advised a temporary quadrupling of the inhaled corticosteroid at the point of asthma deterioration, both of which were actively implemented and supported by local research staff., Primary Outcome: The primary outcome of 'time to first asthma exacerbation' was defined as the need for systemic corticosteroids (for at least 3 consecutive days) and/or unscheduled health-care consultations for asthma (i.e. reaching zone 3 or 4 of the Asthma UK self-management plan)., Results: A total of 1922 participants were randomised: the primary analysis included 938 participants (97%) in the usual-care group and 933 participants (97%) in the modified self-management group. The number of participants having at least one exacerbation of asthma in the year after randomisation was 484 (51.6%) in the usual-care group and 420 (45.0%) in the modified self-management group [adjusted hazard ratio 0.81, 95% confidence interval (CI) 0.71 to 0.92; p = 0.002]. There were fewer serious adverse events reported in the modified self-management group than in the usual-care group (11 vs. 32, respectively). Eight and six events of pneumonia, lower respiratory tract infections or influenza were reported in the usual-care group and the modified self-management group, respectively. Health-care-related costs were lower in the modified self-management group. The modified self-management group was £24 (bootstrapped 95% CI -£122 to £71) less costly than usual care, with a greater quality-adjusted life-year gain of 0.02 (bootstrapped 95% CI -0.005 to 0.04). Therefore, the modified self-management group was 'dominant', with a 94-95% probability of being cost-effective at the £20,000-30,000 threshold., Limitations: As the Fourfold Asthma STudy (FAST) was an open-label pragmatic trial, the possibility of treatment bias that may have affected the participants in the modified self-management group cannot be ruled out. Poorer than expected completion of participant diary cards, particularly within the usual-care self-management group, could have led to a null bias, underestimating the true effect of the intervention., Conclusions: An asthma self-management plan that advises patients to temporarily quadruple their dose of inhaled corticosteroid at the point of asthma symptoms worsening does reduce clinically important asthma exacerbations. In addition, the plan is cost-effective compared with the usual-care self-management plan., Future Work: To effectively implement asthma self-management plans that advise a temporary quadrupling of inhaled steroid at asthma deterioration into routine practice., Trial Registration: Current Controlled Trials ISRCTN15441965., Funding: This project was funded by the NIHR Health Technology Assessment programme and will be published in full in Health Technology Assessment ; Vol. 22, No. 70. See the NIHR Journals Library website for further project information., Competing Interests: David Price reports board membership fees paid to the Observational and Pragmatic Research Institute from Aerocrine AB, Amgen Inc., AstraZeneca plc, C.H. Boehringer Sohn AG & Ko. KG, Chiesi Farmaceutici S.p.A., Mylan N.V., Mundipharma GmbH, Napp Pharmaceutical Group Ltd, Novartis Pharmaceutical Company and Teva Pharmaceutical Industries Ltd; consultancy agreement fees paid to the Observational and Pragmatic Research Institute from Almirall S.A., Amgen Inc., AstraZeneca plc, C.H. Boehringer Sohn AG & Ko. KG, Chiesi Farmaceutici S.p.A., GlaxoSmithKline plc, Mylan N.V., Mundipharma GmbH, Napp Pharmaceutical Group Ltd, Novartis Pharmaceutical Company, Pfizer Inc., Teva Pharmaceutical Industries and Theravance Biopharma; grants from Aerocrine AB, AKL Research and Development Ltd, AstraZeneca plc, C.H. Boehringer Sohn AG & Ko. KG, the British Lung Foundation, Chiesi Farmaceutici S.p.A., Mylan N.V., Mundipharma GmbH, Napp Pharmaceutical Group Ltd, Novartis Pharmaceutical Company, Pfizer Inc., the Respiratory Effectiveness Group, Teva Pharmaceutical Industries, Theravance Biopharma, the UK National Health Service and Zentiva N.V.; lecture/speaking engagement fees paid to the Observational and Pragmatic Research Institute from Almirall S.A., AstraZeneca plc, C.H. Boehringer Sohn AG & Ko. KG, Chiesi Farmaceutici S.p.A., Cipla Ltd, GlaxoSmithKline plc, KYORIN Pharmaceutical Co., Ltd, Mylan N.V., Merck & Company, Inc., Mundipharma GmbH, Novartis Pharmaceutical Company, Pfizer Inc., Skyepharma and Teva Pharmaceutical Industries; manuscript preparation fees paid to the Observational and Pragmatic Research Institute from Mundipharma GmbH and Teva Pharmaceutical Industries; travel expenses fees paid to the Observational and Pragmatic Research Institute from Aerocrine AB, AstraZeneca plc, C.H. Boehringer Sohn AG & Ko. KG, Mundipharma GmbH, Napp Pharmaceutical Group Ltd, Novartis Pharmaceutical Company and Teva Pharmaceutical Industries; funding for patient enrolment or completion of research fees paid to the Observational and Pragmatic Research Institute from Chiesi Farmaceutici S.p.A., Novartis Pharmaceutical Company, Teva Pharmaceutical Industries and Zentiva N.V.; and payment for developing educational materials fees paid to the Observational and Pragmatic Research Institute from Mundipharma GmbH and Novartis Pharmaceutical Company. David Price is a peer reviewer for grant committees for the Efficacy and Mechanism Evaluation and Health Technology Assessment (HTA) programmes. He has stock/stock options from AKL Research and Development Ltd that produces phytopharmaceuticals, and owns 74% of the social enterprise Optimum Patient Care Ltd (in Australia, Singapore and the UK) and 74% of the Observational and Pragmatic Research Institute Pte Ltd (Singapore). Ian Pavord reports grants from GlaxoSmithKline during the conduct of the study; has received speaker’s honoraria from AstraZeneca plc, C.H. Boehringer Sohn AG & Ko. KG, Aerocrine AB, Almirall S.A., Novartis Pharmaceutical Company and GlaxoSmithKline; has received honoraria for attending advisory board panels from Almirall S.A., AstraZeneca plc, C.H. Boehringer Sohn AG & Ko. KG, Dey Pharma, L.P., GlaxoSmithKline, Merck Sharp & Dohme, Schering-Plough, Novartis Pharmaceutical Company, Napp Pharmaceutical Group Ltd and RespiVert Ltd; and has received sponsorship for attending international scientific meetings from AstraZeneca plc, C.H. Boehringer Sohn AG & Ko. KG, GlaxoSmithKline and Napp Pharmaceutical Group Ltd. Mike Thomas received speaker’s honoraria for speaking at sponsored meetings or satellite symposia at conferences from Aerocrine AB, GlaxoSmithKline and Novartis Pharmaceutical Company. He has received honoraria for attending advisory panels with Aerocrine AB, Boehringer Ingelheim, GlaxoSmithKline, Merck Sharp & Dohme, Novartis Pharmaceutical Company and Pfizer Inc. during the conduct of the study. He reports grants from the National Institute for Health Research during the conduct of the study; being a member of the HTA Primary Care Community and Preventative Interventions Panel during the conduct of the study; and personal fees from GlaxoSmithKline, Novartis Pharmaceutical Company, Boehringer Ingelheim and Aerocrine AB outside the submitted work. He is a member of the British Thoracic Society/Scottish Intercollegiate Guidelines Network’s Asthma Guideline Steering Group and the National Institute for Health and Care Excellence’s Asthma Diagnosis and Monitoring Guideline Development Group. Christopher Brightling received payment via his institution of grants and personal fees from AstraZeneca plc/MedImmune, LLC, GlaxoSmithKline plc, F. Hoffmann-La Roche AG/Genentech, Inc., Novartis Pharmaceutical Company, Chiesi Farmaceutici S.p.A., Pfizer Inc., Teva Pharmaceutical Industries, Sanofi S.A./Regeneron Pharmaceuticals, Inc., Glenmark Pharmaceuticals, Mologic Ltd and Vectura Group plc.