Extensive physiological evaluation of lung function were conducted in two groups of asymptomatic individuals with deficiencies of alpha1-antitrypsin: seven subjects with phenotype Pi SZ and six subjects with phenotype Pi Z. Four symptomatic individuals of Pi Z type were also investigated. The asymptomatic individuals of both SZ and Z phenotypes revealed reduction of elastic recoil, hypoventilation and hypoperfusion of the lung bases with increased closing and nitogen wash-out volumes. No signs of bronchial obstruction were observed. The asymptomatic Pi SZ subjects revealed as many signs of subclinical disease as did the asymptomatic Pi Z subjects. These data suggest that Pi SZ subjects are at increased risk of emphysema similar to Pi Z subjects.