Childhood asthma is common and its prevalence is increasing in most countries of the world. Large-scale studies indicate that approximately one-third of children with asthma have had five or more episodes of wheezing in the previous 12 months. Such frequency of symptoms leads to a significant number of days lost from school, interference with physical exercise, and underfunctioning at school because of interrupted sleep. In cases of more severe asthma, the more frequent school absences may affect the individual's education and, possibly, choice of career. In addition to the extensive individual burden of asthma, the burden on the family is substantial. Additional housework may be required to reduce the child's exposure to potential environmental triggers. Time ''off work'' may be required to take care of a sick child. In cases of severe asthma, children regularly wake at night, and 50% of parents indicate limitation of their social life. Sibling studies show that sometimes siblings who do not have asthma are neglected and that parents may have insufficient time to devote to them. Mortality in pediatric asthma is low, but there has been little reduction in recent years. When viewed as potential life-years lost, the burden is considerable in social and economic terms. In the United States, the mean annual cost per patient has been estimated at in excess of US$1,000. In Australia, the cost ranges from A$85 to A$884 per patient, depending on asthma severity. In the United Kingdom the estimated annual costs of childhood asthma to the Health Service are between Β£100 million and Β£150 million. To reduce the burden to patients, their families, and health care services, improved understanding of the basic pathophysiology of asthma is necessary. Environmental issues need to be addressed as does delivery of care using appropriate devices and effective therapeutic medications.