We analyzed continuous nebulized terbutaline (CNT) therapy in 19 patients with 27 admissions for severe asthma and impending respiratory failure who failed to respond to our standard asthma protocol of methylprednisolone, aminophylline, and intermittently nebulized terbutaline. Terbutaline was administered by continuous face mask nebulization at a dose equaling the most frequent previous intermittent dose per hour (4 mg per hour). No patient with frank respiratory failure (i.e., PaCO2 greater than or equal to 60 torr, exhaustion, or coma) was studied. All patients improved, and therapy was stopped in a mean of 15.4 hours (range 3 to 37 hours). The average heart rate did not increase over baseline measurements through 24 hours of CNT. The mean clinical asthma score improved significantly during 8 hours, falling from 6.9 to 3.2 (p greater than 0.001). In 14 patients whose PaCO2 was greater than or equal to 39 torr (range 39 to 58 torr) and clinical asthma score was 6 or greater, PaCO2 decreased a mean of 11.7 torr during a mean of 8.1 hours. In six patients whose PaCO2 was 45 torr or greater at the start of CNT (mean 49, range 45 to 58 torr) and in whom we would have previously treated with intravenous isoproterenol, PaCO2 decreased a mean of 15 torr in an average of 8.7 hours. This preliminary study suggests that CNT is an effective therapy for severe asthma in children.