Objective: The objective of this trial was to determine the efficacy of frequent nebulized ipratropium added to high-dose albuterol therapy in children with severe asthma. Methods: One hundred twenty children (5 to 17 years) of age) with severe acute asthma (forced expiratory volume in 1 second [FEV1], <50% of the predicted value) were enrolled into a randomized double-blind three-arm placebo-controlled trial comparing three groups: group 1, three doses of nebulized ipratropium bromide within 60 minutes (250 μg/dose); group 2, one dose of ipratropium; group 3, no ipratropium. All patients were also treated with three doses of nebulized albuterol within 60 minutes (0.15 mg/kg per dose). Pulmonary function and clinical measures were assessed every 20 minutes for up to 120 minutes. Results: The groups were comparable at baseline. At 120 minutes, the mean percentage of predicted FEV1 improved from 33.4% to 56.7% in group 1, from 34.2% to 52.3% in group 2, and from 35.4% to 48.4% in group 3 (p = 0.0001). The differences between groups were larger in those children with a baseline FEV1 ≤30% of the predicted value: FEV1 increased from 24.5% to 50.9% in group 1, from 25.0% to 39.8% in group 2, and from 25.9% to 36.5% in group 3 (p = 0.0001). In group 1, 38% of the patients were hospitalized after the study, 44% in group 2, and 46% in group 3 (p value not significant). However, in patients with FEV1 ≤30%, the hospitalization rates were 27% in group 1, 56% in group 2, and 83% in group 3 (p = 0.027). There were no toxic effects attributable to ipratropium. Conclusion: The addition of repeated doses of nebulized ipratropium to frequent high-dose albuterol therapy in patients with acute severe asthma is both safe and more effective than albuterol alone; its use in patients with very severe asthma may reduce hospitalizations. (J PEDIATR 1995;126:639-45)