In a study of early-life risk factors for the development of adult obstructive airway disease, respiratory symptoms, disease and smoking histories, and spirometry were obtained for 650 children 5 to 9 yr of age and their families in East Boston, Massachusetts. Persistent wheezing was the most frequently reported chronic symptom, occurring in 9.2% (60/650) of the population. Children with persistent wheezing were more likely to report cough and phlegm (p < 0.001), a history of asthma (p < 0.001), hay fever (p < 0.02), or past hospitalization with a respiratory illness (p < 0.001) than their asymptomatic peers. Prospective evaluation of a subsample of the 650 children confirmed a greater occurrence of acute lower respiratory illness in those children with persistent wheeze. Parental cigarette smoking was linearly related to the occurrence of persistent wheezing (p = 0.012) and lower degrees of mean normalized forced expiratory flow during the middle half of the forced vital capacity (FEF-Z score). A multiple linear regression identified the mother's current smoking status and current persistent wheeze as significant predictors of the children's mean FEF-Z score. Other variables, such as the father's smoking, children's personal smoking, a doctor's diagnosis of asthma, and a past history of lower respiratory illness were not significant predictors of the FEF-Z score.