About 334 million people worldwide suffer from asthma, and this figure may be an underestimation. It is the most common chronic disease in children. Asthma is among the top 20 chronic conditions for global ranking of disability-adjusted life years in children; in the mid-childhood ages 5-14 years it is among the top 10 causes. Death rates from asthma in children globally range from 0.0 to 0.7 per 100 000. There are striking global variations in the prevalence of asthma symptoms (wheeze in the past 12 months) in children, with up to 13-fold differences between countries. Although asthma symptoms are more common in many high-income countries (HICs), some low- and middle-income countries (LMICs) also have high levels of asthma symptom prevalence. The highest prevalence of symptoms of severe asthma among children with wheeze in the past 12 months is found in LMICs and not HICs. From the 1990s to the 2000s, asthma symptoms became more common in some high-prevalence centres in HICs; in many cases, the prevalence stayed the same or even decreased. At the same time, many LMICs with large populations showed increases in prevalence, suggesting that the overall world burden is increasing, and that therefore global disparities in asthma prevalence are decreasing. The costs of asthma, where they have been estimated, are relatively high. The global burden of asthma in children, including costs, needs ongoing monitoring using standardised methods.