Cystic fibrosis patients and their parents have increased alpha-adrenergic sensitivity, increased cholinergic sensitivity, and reduced beta-adrenergic sensitivity. This combination of autonomic aberrations has been associated with increased airway reactivity in other disease populations. Although studies of airway reactivity are difficult to interpret in the cystic fibrosis patients themselves, the parents have no apparent pulmonary infection or inflammation, and one-third of these people have increased airway reactivity. Moreover, parents of children with cystic fibrosis have increased prevalence of wheezing and lung disease in childhood. Airway reactivity has been associated in other populations, with increased risk of obstructive pulmonary disease. Further studies are required to test the hypothesis that heterozygosity for CF is a risk factor for development and progression of obstructive pulmonary disease.