OBJECTIVE To evaluate the efficacy of aerosolized adrenaline compared to inhaled beta(2) agonists in the treatment of acute asthma in the emergency setting. DATA SOURCES MEDLINE, EMBASE, CINAHI, and Cochrane databases, review articles, and references of included trials. REVIEW METHODS Published (1966-2005) randomized controlled trials with pulmonary function as primary outcome. RESULTS Six studies met the criteria for inclusion in the meta-analysis. They included 161 adults and 121 children and adolescents. Patients who received inhaled adrenaline showed a nonsignificant improvement in pulmonary function (standardized mean difference = 0.20, 95% confidence interval -0.22 to 0.63, P = .35) compared to patients getting inhaled beta(2) agonists. Moderate heterogeneity was identified between studies (I(2) = 47.2%). Homogeneity was achieved when studies that reported pulmonary function were stratified by intensity of adrenaline treatment. The use of more than 2 mg of adrenaline per dose was equivalent to 5 mg of salbutamol or terbutaline per dose. On the contrary, 2 mg or less of adrenaline per dose was inferior to 2.5 or 5 mg of salbutamol per dose. In addition, there were no differences in heart rate and Pao(2) between treatments. CONCLUSIONS There was no statistically significant benefit of nebulized adrenaline over salbutamol or terbutaline in the treatment of children and adults with moderate-severe acute asthma.