During the past few years findings from two studies—the International Study of Asthma and Allergies in Childhood (ISAAC)1 and the European Community Respiratory Health Survey (ECRHS)2—seem to have dominated much of the thinking about the geographical variations in the prevalence of asthma. These studies suggest important variations by geographical site in different countries and, to a lesser extent, in study centres within countries. However, these studies only raise new questions as to how geographical factors contribute to the aetiology of asthma. For example, are the geographical variations in the prevalence of asthma caused by unique exposures to disease causing agents found only in local environments? Do differences in geographical location in some way alter host susceptibility? Do local environmental conditions, either physical or sociocultural, alter the host/agent interactions in ways that are critical to the expression of this condition?

In this issue of Thorax Duran-Tauleria and Rona3 further elucidate how social and physical environmental factors may explain some of the geographical expression of asthma prevalence. Their study focuses on the differences in asthma and respiratory symptoms among three populations—two nationally representative samples of English and Scottish children and a third sample of children living within the inner cities of …