To determine the response to nebulized beta 2 agonist, 28 children younger than 2 years of age who visited the emergency department during an episode of acute asthma were studied. Each subject had a previous history of recurrent wheezing episodes. They were randomly assigned to receive two administrations of either nebulized albuterol (0.15 mg/kg per dose) or placebo (normal saline) with oxygen, 1 hour apart. After two nebulizations, the albuterol-treated patients had a greater improvement in clinical status (respiratory rate, degree of wheezing and accessory muscle use, total clinical score, and arterial oxygen saturation) than the placebo group. None of the patients in the albuterol group experienced a decrease of arterial oxygen saturation of greater than or equal to 2%. It is concluded that a trial of nebulized beta 2 agonists is warranted in the treatment of acute asthma in infants and young children.