Fluticasone propionate is a synthetic steroid for use by the inhaled route. It's high topical potency and low systemic bioavailability make it suitable for use in asthmatic children. A total of 258 children were randomised in a double-blind study to receive fluticasone propionate (50 micrograms bd) as the dry powder formulation inhaled via a Diskhaler inhaler, or matched placebo (with current therapy) for 4 weeks throughout which time diary cards were completed. During clinic visits lung function and adrenal function were measured. Fluticasone propionate produced a significantly greater increase in morning peak expiratory flow rate (PEFR) (adjusted mean difference over days 1-28, 17 l/min (95% CI; 10, 24); P < 0.001) and evening PEFR (adjusted mean difference over days 1-28, 16 l/min (95% CI; 9, 23); P < 0.001). In addition, diary card symptom scores, beta 2-agonist rescue and clinic lung function improved significantly on fluticasone propionate. There were few adverse events and basal plasma cortisol remained within the normal range. In conclusion fluticasone propionate at 50 micrograms bd is superior to placebo (current therapy) in the treatment of childhood asthma with no evidence of adverse effects.