We enrolled 30 infants (median age 3 months, range 1-12 months), hospitalized for bronchiolitis in a randomized double-blind trial, to examine the efficacy and safety of nebulized epinephrine compared to salbutamol. Once admitted, patients were treated with either nebulized 0.5 mg of an 0.1% epinephrine solution (0.5 mL in 3.5 mL normal saline (NS)) or 2.5 mg nebulized salbutamol (0.5 mL in 3.5 mL NS). They were evaluated daily before and after nebulization until discharge. The outcome measures used were: baseline clinical score (based on respiratory rate, subcostal retraction, presence of wheezing, and O2 requirement), change in clinical O2 score after nebulization, duration of O2 therapy, and duration of hospitalization. A significant improvement in the clinical score was noted on the first day of hospitalization in subjects receiving epinephrine (P = 0.025); that change was not seen in those on salbutamol (P = 0.6). Nebulized epinephrine decreased the baseline clinical score faster than salbutamol (P = 0.02), though on the fourth study day there was no significant difference between the two scores. On the fourth and fifth days of study there were more patients hospitalized in the salbutamol group than in the epinephrine group (P = 0.03 vs. P = 0.025). No adverse effects were associated with nebulized therapy. We conclude that nebulized epinephrine is a more effective agent than salbutamol in the initial treatment of bronchiolitis and is equally safe.