Seven patients with a severe deficiency of α1-antitrypsin have been studied. These patients represented three families; four were female and three were male. Although two were asymptomatic, they all demonstrated obstructive pulmonary disease, low carbon monoxide diffusing capacity, hypoxia, and elevated alveolo-arterial PO2 gradients. Hypercapnia was present in one patient. Chest films and lung scans demonstrated decreased vascularity in the lower lung fields. These findings are consistent with panacinar emphysema, and no evidence of bullous emphysema was found. The onset of symptoms at an early age, equal sex incidence, and the above features characterize the syndrome of familial α1-antitrypsin deficiency and chronic lung disease.