Asthma is a disease needing urgent action. Morbidity and mortality are rising, despite advances in our understanding of asthma and in its treatment. The lifetime prevalence of asthma in children varies from 5 to 31%, depending on the defining criteria, and even when recent prevalence (occurring in the past two years) is examined, rates from 5 to 18% have been found. There is growing evidence which shows that signs of reversible airways disease occur in the elderly with even greater frequency and it is likely that at least 10% of the population will need asthma treatment at some stage of their lives; this means that well over five million people in the UK or 250 patients in each 'average' general practice list of 2500 merit the diagnosis of asthma at some stage of their lives. The fact that an average practice is likely to have diagnosed less than half that number clearly implies that asthma is first and foremost an under-diagnosed disease.