This study of a general population sample reveals close relationships between histories of childhood respiratory disorders and pevalences of symptoms, obstructive airway diseases, and ventilatory impairment in 2,626 adults more than 20 years of age. Although a history of pediatric respiratory illness is associated with relatively mild impairment of ventilatory function in young adults, subjects with such a history shown an excessive decline in function with advancing years and with cigarette use. Because some of the data are retrospective and subject to the bias of preferential recall of childhood events, these observations cannot be regarded as definitive. However, present observations are compatible with the hypothesis that pediatric respiratory illness represents an important risk factor for the development of obstructive airway diseases in adult life. It is suggested that these childhood respiratory illnesses cause the adult lung to be unusually susceptible to the adverse effects of a variety of bronchial irritants and infectious agents.