Guidelines for managing asthma in pediatric patients published by the American Academy of Allergy, Asthma, and Immunology and the American Academy of Pediatrics recommend the use of inhaled corticosteroids for the management of persistent asthma in infants and young children. When these guidelines were published, pressurized metered-dose inhalers and dry-powder inhalers were the only delivery devices available for inhaled corticosteroids in the United States. These devices can be difficult for young children to use correctly. Furthermore, no inhaled corticosteroid was approved in the United States for the treatment of children younger than 4 years. Budesonide inhalation suspension (Pulmicort Respules; AstraZeneca LP, Wilmington, Del) was developed to meet the medication delivery needs of infants and young children with persistent asthma. Pulmicort Respules is the first inhaled corticosteroid approved for administration by means of a nebulizer and the only inhaled corticosteroid approved in the United States for infants as young as 12 months. Budesonide has been studied extensively worldwide. In the United States the tolerability and efficacy of budesonide inhalation suspension were confirmed in 3 placebo-controlled multicenter trials. These studies demonstrated that both once- and twice-daily dosing of budesonide inhalation suspension (0.25-1 mg) improved pulmonary function and ameliorated asthma symptoms in infants and young children with persistent asthma. Budesonide inhalation suspension was well tolerated, and the incidences of reported adverse events were similar among patients in the budesonide, placebo, and conventional asthma therapy groups. This article reviews the results of these studies, as well as the pharmacokinetics, pharmacodynamics, and clinical use of budesonide inhalation suspension.