Twenty-eight members of one family were investigated for the presence of pulmonary disease concurrent with variable (ZZ, MZ, or MS) degrees of alpha-1 antitrypsin deficiency. Three symptomatic siblings (2, ZZ; 1, MZ) had abnormal pulmonary scans and abnormal routine pulmonary function studies. Five asymptomatic heterozygotes, three of whom had never smoked and were the youngest studied, had distinctly abnormal closing volumes. Three of the five patients also had abnormal perfusion dynamics when scanning was done in the upright position. Pulmonary dysfunction occurs in asymptomatic heterozygotes but requires the use of sensitive techniques for its appreciation.