Ninety children with acute asthma, equally divided into two study groups, were studied to compare the efficacy and safety of nebulized terbutaline with injected epinephrine in the treatment of acute exacerbation. The terbutaline group received 2 ml (5,0 mg) terbutaline solution diluted with 2 ml 0.9% saline for inhalation over 10 minutes; the epinephrine group received 0.01 ml/kg of 1:1000 epinephrine (maximum 0,3 ml) through subcutaneous injection at deltoid area. Spirometry, pulse oximetry, and clinical severity scoring system were evaluated at baseline and again 15 minutes after treatment. The baseline data of the two groups were not significantly different. The clinical severity score and spirometry of both groups were significantly improved after treatment. Compared with the terbutaline group, the epinephrine group had better mean oxygen saturation (SaO2; p < 0.001), frequency of oxygen desaturation (p = 0.0028) and forced expiratory flow 25-75% (FEF25-75%, p = 0.027). For those patients with initial forced expiratory volume in one second (FEV1) lower than 60% of predicted value, epinephrine treatment was more effective in the improvement of FEV1, FEF25-75%, and oxygen saturation (SaO2) (p = 0.011, 0.012, and 0.006, respectively). A Significantly higher rate of adverse effects occurred in patients given epinephrine (47% vs 11%, p = 0.0002); these included pallor, tremor, dizziness, headache, palpitation, soreness of legs, numbness of extremities, cold sweating, general weakness and nausea. Considering the general trend to noninvasive therapy in children and the more frequent adverse effects after epinephrine injection, such nebulized beta-2 agonists as terbutaline appear preferable for initial therapy of acute asthma if oxygen is supplemented to prevent possible hypoxemia. However, parenteral epinephrine still is worth trying, particularly in any severe, life-threatening attack.