The objective of the proposed large, high-intensity, randomised controlled trial is to evaluate the real-life effectiveness of providing a written action plan to asthmatic children discharged from the emergency department (ED) or hospital on the short-term adherence to written recommendations (including medication, attendance to asthma education and medical follow-up). Contrary to the traditional definition of a written action plan,1 i.e., a set of written instructions to follow in case of an exacerbation, we propose to test a new written action plan based on the innovative concept that emphasises the key elements associated with good asthma care: (1) use of preventive medication, (2) need for asthma education, (3) need for regular medical review, (4) environmental control and (5) instructions for use of rescue medication. The main outcome is adherence to prescribed inhaled preventive medication measured by an electronic counter. Secondary outcomes include attendance to asthma education and to medical follow-up, serving by pharmacy of prescription of oral steroids, as well as asthma control measured by questionnaire (Asthma Quiz for Kidz),2 use of rescue ß2-agonists, relapse to emergency room. Because of the recommended medical follow-up where primary care physicians may recommend a change in the preventive treatment initiated in hospital, only short-term outcomes occurring within 28 days of the index visit will be considered as associated with the use of the written action plan. We have purposely designed this trial to test the additional benefit of the intervention over the usual care, recognizing the heterogeneity in the amount of asthma information provided within the time constraints of the emergency room by our 90 physicians. To provide clinically meaningful and generalisable information, the eligibility criteria for study entry have been limited to the bare necessity to confirm the diagnosis of asthma. The randomisation will be stratified on age to reflect the target interlocutor of the written action plan, namely the parents for the 60% children aged < 6 years, the child and parent pair for the 40% children aged 7 to 12 years old, and the adolescents for the 10% patients aged 13-17 years old. We anticipate important variations in the characteristics of enrolled patients reflecting the real heterogeneity of the emergency department attendees, namely in the severity of baseline exacerbation (55% mild, 35% moderate, 10% severe), ownership of a written action plan (15%), prior asthma education (30%), use of daily preventive medicine (25%), etc, all of which may influence the adherence rate to the written action plan. To compensate this heterogeneity in patients' characteristics and provided instructions, the power of the trial to identify a clinically important difference in the main outcome has been set at 90% rather than the traditional 80%. The strength of the proposed study is clearly the assessment the real-life effectiveness of providing a new concept written action plan to a high-risk population to improve the main obstacles to good asthma control, namely adherence to preventive medication and attendance to asthma education and regular review.