The incidence, clinical manifestations, and infectious etiology of respiratory illnesses observed in a prospective longitudinal study were correlated with serum IgE values, which were used as objective markers of atopy. The incidence of wheezing illnesses was greater in children with elevated IgE levels, confirming an association previously reported. In contrast, the incidence of upper respiratory illness or middle ear disease showed no correlation with IgE values. The number and types of viral infections distributed evenly throughout the population. The results suggest that children with recurrent URI or MED deserve evaluation for allergy only if there are other clinical findings suggestive of atopy.