Wheezing lower respiratory tract illness in infancy and asthma share the clinical findings of wheezing and respiratory distress. Although the link between wheezing lower respiratory tract illness in infancy and the subsequent development of asthma is a limited one, both conditions do share some common risk factors, including exposure to environmental tobacco smoke, difficult living conditions (low socioeconomic class, crowding, allergen exposure), and increased risk in males. The impact of baseline lung function on wheezing lower respiratory tract illness risk is substantial and may be independent of airway reactivity. In contrast, the development of chronic airway inflammation mediated by allergic sensitization plays a central role in the development of persistent asthma. Although the endogenous risks for these two outcomes may be fixed, it is clear that caregivers may help to reduce or eliminate the exogenous risks listed earlier by parental education and improvement of the living conditions of young children.