In a double-blind, randomized, parallel-group clinical trial, 340 asthmatic patients aged 12-70 years received budesonide 400 micrograms once daily in the morning, budesonide 400 micrograms once daily in the evening, budesonide 200 micrograms twice daily or placebo, for 12 weeks in addition to inhaled short-acting beta 2-agonists used as required (p.r.n.). Budesonide was given as Pulmicort Turbohaler. Peak expiratory flow rate (PEFR) increased by 20 to 30 1 min-1 in each of the active treatment groups, significantly more than in the placebo group (P < 0.01). There were no significant differences between the active treatment groups. Symptom improvement and decreased beta 2-agonist use reflected the PEFR data. Incidences of adverse events in the active treatment groups were similar to those observed in the placebo group. Budesonide 400 micrograms given once daily morning or evening is equieffective with the same total daily dose given twice daily in the treatment of mild to moderate stable asthmatics.