The relative clinical efficacy and systemic effects of different inhaled corticosteroids is controversial. To obtain further information on this matter, the authors have performed meta-analysis of seven trials comparing fluticasone propionate (FP) with budesonide (Bud), and seven trials comparing FP with beclomethasone dipropionate (BDP) for the treatment of asthma of all severities in adult and paediatric patients. In all cases, the drugs were compared at clinically equivalent doses, i.e. FP was given at half (or less) the microgram dose. The total number of patients was 1980 (1000 treated with FP 200-800 micrograms day-1 and 980 with Bud 400-1600 micrograms day-1), and 1584 patients in the second analysis (780 treated with FP 200-1000 micrograms day-1 and 804 with BDP 400-2000 micrograms day-1). FP significantly improved mean morning peak expiratory flow rate (PEFR) compared with Bud, with an overall difference of +11 l min-1. Analysis of serum cortisols showed no differences between FP and Bud treatment at low doses, but at higher dosages, and overall, significant differences in favour of FP were observed. In the second meta-analysis, no significant differences in PEFR were observed between FP and BDP in any of the seven individual studies or in the pooled analysis. Analysis of serum cortisols showed a similar trend to the previous analysis, however, no overall difference in serum cortisol results were seen between FP and BDP. In conclusion, the pooled analysis shows that FP at half the dose (or less) is more effective than Bud and as effective as BDP in improving PEFR; in addition, these improvements were achieved with a reduction in cortisol suppression compared with BUD and with no greater degree of cortisol suppression compared with BDP. This demonstrates, in patients with asthma, that FP has an improved efficacy to safety ratio compared with older inhaled corticosteroids.