Twenty-seven asthmatic outpatients were randomly treated with bambuterol 30 mg administered once daily before going to bed and sustained release terbutaline 10 mg twice daily in a 14 day, double blind cross over study. On all the parameters of bronchodilator effects, namely peak expiratory flow rate (PEF), use of extra beta-agonist puffs, asthma symptom score, and patient preference for one of the treatments, no statistically or clinically significant difference between the two treatments was found. No significant difference between treatments was observed in the number or severity of side-effects. Bambuterol administered once daily appears to be an effective anti-asthmatic treatment.