In a double-blind, placebo-controlled trial, 40 infants between 6 weeks and 24 months of age who had a first episode of wheezing and other signs and symptoms of bronchiolitis were randomly assigned to receive either nebulized albuterol (0.15 mg/kg/dose) or placebo (saline solution) for two administrations 1 hour apart. The albuterol therapy resulted in a significantly greater improvement in the accessory muscle score (decreases 0.70 vs decreases 0.30; p = 0.03), oxygen saturation (increases 0.71% vs decreases 0.47%; p = 0.01) after one dose, and in the accessory muscle score (decreases 0.86 vs decreases 0.37; p = 0.02), respiratory rate (decreases 19.6% vs decreases 8.0%; p = 0.016), and oxygen saturation (increases 0.76% vs decreases 0.79%; p = 0.015) after two doses of the drug. The response to therapy was similar in infants younger and those older than 6 months of age. The heart rate rose slightly more in the albuterol group (increases 7.76 from baseline) versus the placebo group (decreases 6.79). There were no other side effects of the treatment. Of the 34 children from whom nasal specimens were obtained by swab for viral identification, 24 had positive test results (21 for respiratory syncytial virus, 1 for parainfluenza, 1 for paramyxovirus, and 1 for influenza A). We conclude that nebulized albuterol constitutes a safe and effective treatment of infants with bronchiolitis.