Croup and acute bronchiolitis are common forms of virally induced respiratory disease in infancy and early childhood. There is good evidence that corticosteroids can ameliorate disease severity and alter the natural history of symptoms in patients who have croup and that temporary symptomatic benefit can be obtained from the use of nebulized adrenaline. The principle weakness when reviewing therapeutic interventions for acute bronchiolitis is the lack of a clear diagnostic test or definition. Current evidence suggests that oxygen is the only useful pharmacologic agent for correcting hypoxia.