To compare the bronchodilation and adverse effects of two commercially marketed short-acting beta2-adrenergic agonists, terbutaline (Bricanyl, 5.0 mg/2ml) and fenoterol (Berotec,1.25 mg/2ml) unit dose vials (UDV), 108 acute asthmatic children, aged 5 to 14, were randomly enrolled into this study. Nebulization treatment for 10 minutes using an air compressor nebulizer was performed after measurements of baseline spirometry, SaO2, blood pressure and pulse rate. Same measurements were repeated at 0, 5, 15 and 30 minutes after the end of the nebulization treatment. The blood pressure was also monitored immediately and 30 minutes after treatment. Almost all the spirometric parameters of both treatments at various time points significantly improved. The pulse rate significantly increased at 15 and 30 min. The SaO2 significantly increased at 30 min. The systolic blood pressure significantly decreased immediately (terbutaline only) and at 30 min (fenoterol only). No significant change was found in diastolic blood pressure. When the laboratory parameters at the same time points were compared. Significant better results for fenoterol treatment were found in FEV, at 30 min (p = 0.048), PEF at 15 and 30 min (p = 0.049 and p = 0.027, respectively), FEF25-75% at 30 min (p = 0.033), mean absolute increase of PEF at 15 min (p = 0.034) and 30 min (p = 0.021), FEF25-75% at 30 min (p = 0.046), and in mean percent increase of FEF25-75% at 30 min (p = 0.047). The adverse effects for both groups were almost equal and around 21%. In conclusion, both terbutaline and fenoterol UDV nebulization treatments are effective in treating acute asthmatic children. The adverse effects are nearly equal. The fenoterol UDV nebulization treatment shows a little better result in improving pulmonary function than does terbutaline.