Asthma prevalence is increasing worldwide, and there is growing concern about the burden of asthma both for patients and for the health sevices. There have also been major changes in the way in which the management of asthma death in some western countries in the 1960's and again in the 1970's. Asthma epidemiology has a major role to play in investigating the causes of these global changes, and in developing preventive interventions. This is the first...