The relationship between parental antecedents of respiratory disease and actual home exposure to smoking and pets was studied in a population of 2,000 children and adolescents with respiratory disease, presumably of allergic origin. No significant differences were observed in the frequency of home exposure to smoking and pets whether the children had unilateral, bilateral or no parental antecedents of respiratory disease. Thus, from this study there appears to be no evidence to suggest that a personal history of respiratory disease leads parents to apply better preventive measures at home for their children.