One hundred and sixty seven children on 0-200 microgram/day of inhaled steroid with asthma symptoms and sub-optimal peak flow values (less than 90% of that predicted for their height) were randomly allocated either 400 microgram once daily (nocte with placebo o.m.) or 200 mircrogram twice daily of budesonide Turbohaler for 8 weeks. Bronchdilator usage and symptoms were reduced in both groups at 4 and 8 weeks compared with baseline. There was a significant increase within both groups in morning and evening PEF after 4 and 8 weeks. The increase in evening PEF after 8 weeks was greater in the once-daily group than in the twice-daily group but there were no other significant differences between the groups (morning: +24.6 l/min vs 15.2 l/min, p = 0.059; evening: + 19.7 l/min vs +8.31 l/min; p = 0.013). Budesonide Turbohaler 400 microgram once daily is therefore as effective as 200 microgram twice daily in achieving asthma control in children.