The incidence of pulmonary emphysema in patients with alpha-1-antitrypsin (α-1-AT) deficiency associated with the protease inhibitor (Pi) phenotype ZZ is increased. To determine wheter less severe deficiency states of α-1-AT (i.e. Pi phenotypes other than ZZ and MM) might predispose to the development of pulmonary disease, Pi phenotypes were determined in a group of patients in whom the incidence of chronic pulmonary disease is high. The proportion of 52 patients with Sjögren’s syndrome who had Pi phenotypes other than ZZ and MM was not significantly greater than that for populations of normal subjects. Mean values for tests of pulmonary function, including estimates of both restrictive lung disease and airway obstruction in patients with the MM phenotype were not significantly different from corresponding means for patients with non-MM phenotypes. These findings suggest that the increased susceptibility of patients with Sjögren’s syndrome to develop chronic obstructive pulmonary disease is not attributable to an abnormally high frequency of non-MM phenotypes and associated moderately reduced serum levels o