Aminophylline is routinely recommended as a basic part of the emergency treatment of asthma. A comprehensive search found 13 reports of controlled trials of intravenous aminophylline therapy in severe, acute asthma. These studies compared aminophylline therapy with treatment with either albuterol (salbutamol), epinephrine, or other bronchodilators. The 13 reports did not agree. Seven reported no difference in spirometric values between aminophylline treatment and the control regimens. Three found aminophylline treatment superior. Three favored the control regimen. The results of the 13 trials were reanalyzed and pooled. Overall, there was no difference between the aminophylline-treated groups and the control groups. Sensitivity analysis suggests that aminophylline therapy is ineffective alone but may be more effective than single-drug therapy when combined with an injected beta-agonist. Despite widespread practice, available trials do not provide adequate evidence to support or reject the use of aminophylline in the treatment of severe, acute asthma.