Inhaled corticosteroids are highly effective in the treatment of asthma at all ages and their use in younger children is increasing. As concerns exist about the long-term systemic side-effects of high dose inhaled corticosteroids, current guidelines continue to recommend sodium cromoglycate (SCG) as first line regular medication for children with frequent symptoms. Few published studies have compared the safety and efficacy of inhaled corticosteroids with SCG in children. This study compares SCG with the new inhaled corticosteroid, fluticasone propionate (FP), which has theoretical advantages over other currently available corticosteroids due to its negligible oral bioavailability. This was a randomized, open, multi-centre, parallel group comparison of 50 micrograms FP twice daily and 20 mg SCG four times daily over 8 weeks, preceded by a 2-week baseline period. Sixty-two general practices and two hospital centres enrolled 225 asthmatic children aged 4-12 years (110 received FP; 115 received SCG). Outcome measures improved in both groups, with a significant difference in favour of FP for the key variables of mean morning and evening % predicted PEFR and % of symptom-free days and nights. No significant difference was observed for FEV1, or relief medication use. Two children taking FP and 10 children taking SCG withdrew because of adverse events. This study showed that low dose FP was effective and superior to SCG in young children with mild-moderate asthma. Safety studies of longer duration are needed before changing the current recommendations for inhaled corticosteroid therapy.