Inhaled corticosteroids form the cornerstone of treatment for most patients with asthma. A range of compounds are available with a wide range of prescribable doses. In this overview, we summarize the findings from a number of Cochrane systematic reviews that have examined the relative benefits of different doses of beclometasone dipropionate, budesonide and fluticasone propionate when used to treat children and adults. The key findings are that all inhaled corticosteroids demonstrate a dose-response relationship for efficacy measures, but most of the benefit in mild-to-moderate severity disease is gained in the low-to-moderate dose range of each drug. In this group, high doses of fluticasone lead to small improvements in measures of control at the expense of a steep increase in the incidence of oral side-effects. In patients with severe disease who are dependent on oral steroids, there may be appreciable benefit in reducing oral steroids from very high compared with high doses of fluticasone.