High-dose nebulized albuterol is standard therapy for severe asthma exacerbations at The Children's Hospital of Philadelphia (CHOP) and other tertiary care pediatric hospitals throughout the United States. For the most severe exacerbations, albuterol is provided continuously at high doses until improvement is observed. This regimen has been standardized in a treatment protocol that has been used at CHOP for more than 5 years. Recently, levalbuterol (LEV), the purified active (R)-enantiomer of albuterol, has been approved for use in acute asthma. Preliminary evidence suggests that LEV may improve pulmonary function and clinical outcomes in children with asthma based on studies using standard dosing regimens. Laboratory and clinical evidence suggest that the (S)-enantiomer of albuterol may have detrimental effects that contribute to poor response to racemic albuterol (RAC). Limited data exist about the efficacy of LEV in high-dose regimens.