<p>ASTHMA IS a common condition, reportedly affecting as many as one in five school-age children (Kaur et al 1998). For many, its effects are mild, although it can be serious and even life-threatening. Recent publications appear to provide conflicting information on asthma prevalence. On the one hand, we are told that the prevalence of asthma has doubled (Upton et al 2000), only to learn a few weeks later that it has been in decline since 1993 (Fleming et al 2000a). This short report aims to explain the reasons for this apparent contradiction.</p>