The aim of this study was to examine the dose-response relationship of inhaled budesonide in adolescents and adults with asthma. A meta-analysis was carried out on placebo-controlled, randomised clinical trials, presenting data on at least one outcome measure of asthma and using at least two doses of budesonide, delivered by turbuhaler or metered-dose inhaler + spacer twice daily. A total of six studies of 1,435 adolescents and adults, with mild to moderately severe asthma, met the inclusion criteria for the meta-analysis. A negative exponential model indicated that 80% of the benefit at 1,600 micrograms.day-1 was achieved at doses of approximately 200-400 micrograms.day-1 and 90% by 300-600 micrograms.day-1. Meta-regression with a quadratic term in dose showed that the maximum effect was obtained with doses of approximately 1,000 micrograms.day-1. In conclusion, the available published data indicate that, in adolescents and adults with mild to moderate asthma, most of the therapeutic benefit of budesonide delivered by turbuhaler or metered-dose inhaler + spacer is achieved with a dose of approximately 400 micrograms.day-1 and the maximum effect is achieved at approximately 1,000 micrograms.day-1. This conclusion is qualified by the recognition that there is considerable individual variability in the response to inhaled corticosteroids and that the subjects included in this meta-analysis had predominantly mild to moderate asthma.