Forty-four Pediatric Intensive Care Unit (PICU) admissions for acute severe asthma in 27 children between 8/80 and 10/86 were reviewed to determine the safety of prolonged administration of frequently nebulized terbutaline. The mean dose of nebulized terbutaline was 0.2 mg/kg/dose (range = 0.1 to 0.4 mg/kg/dose) given at a mean frequency of 2.4 +/- 1.2 hours. Seven patients received continuous nebulization at a dose of 0.4 +/- 0.2 mg/kg/h. All patients were placed on continuous cardiorespiratory monitoring. Emergency room therapy was determined by the primary emergency room physicians. Upon admission to the PICU, the mean +/- SD heart rate was 150 +/- 21 bpm and the respiratory rate was 44 +/- 16 bpm. After institution of therapy, these parameters decreased to a similar degree in parallel. The maximum decrease after 36 hours was 28% and 37% for heart rate and respiratory rate, respectively. No cardiac arrhythmias were noted. The initial PaCO2 upon admission to the PICU was 32 mm Hg (range = 24 to 44 mm Hg), the maximum decrease in PaCO2 generally occurred during the 6-hour to 12-hour time interval following admission. We conclude that frequent administration of high doses of nebulized terbutaline is safe in the management of acute severe childhood asthma even in the setting of prolonged administration to the hospitalized child.