This study evaluated the administration of albuterol syrup (0.1 mg/kg/6 hr) or placebo to 2- to 6-year old children whose extrinsic asthma was treated with maintenance theophylline in a prerandomized, double-blind crossover study design. Albuterol/theophylline treatment produced peak expiratory flow rates 2 hours after administration that were significantly higher than in the theophylline/placebo-treated group (119.3 L/min versus 83 L/min) p less than 0.01. The theophylline/placebo-treated group also required higher serum concentrations of theophylline to control wheezing, 10.5 micrograms/ml versus 5.0 micrograms/ml (p less than 0.01). The average symptom scores for the albuterol/theophylline-treated patients (72.5) were less than that of theophylline/placebo-treated group (97.6) p less than 0.02. Side effects such as tremor, irritability, or insomnia occurred in only two of 17 patients. Serial EKG recordings demonstrated no evidence of cardiotoxicity, such as arrhythmias, or indication of myocardial injury. The addition of albuterol to theophylline improved control of severe asthma in children 2 to 6 years of age demonstrated by improvement in pulmonary function, decrease in theophylline dosage requirement, and improvement in symptoms. It was free of any known cardiotoxicity.