The subjects were 40 children aged 6 to 16 years with stable chronic asthma; 20 were randomly assigned to receive 40 micrograms/kg of tulobuterol twice daily and 20 received 100 micrograms/kg of albuterol three times daily for three months. Patients were assessed by spirometry after the morning dose of medication at 0, 2, 4, 8, and 12 weeks of treatment. After initial dosing, the mean percentage increases in forced expiratory volume in one second (FEV1) were significantly higher in the tulobuterol-treated patients than in the albuterol-treated patients: at 30 minutes after dosing, the mean increase was 17.2% in the tulobuterol group and 5% in the albuterol group; at one hour, 20.3% and 6.8%. Similar results were found at 12 weeks. Mean changes in forced vital capacity and peak expiratory flow rate were similar to the changes in FEV1. Treatment side effects were reported by seven tulobuterol-treated patients and by four albuterol-treated patients. Tulobuterol treatment was withdrawn in one patient because of severe vomiting and headache of unknown cause. No changes in cardiovascular function were found in any patient. It is concluded that tulobuterol taken twice daily was more effective than albuterol taken three times daily in the treatment of asthma in children.