Alpha 1 antitrypsin deficiency predisposes subjects to developing pulmonary emphysema and childhood liver cirrhosis. We have studied restriction fragment length polymorphisms (RFLPs) of the alpha 1 antitrypsin gene in a normal population and a group of patients with pulmonary emphysema. We have identified five RFLPs with eight restriction enzymes. The most frequent polymorphisms have been detected with the enzymes MspI, PstI, and TaqI at frequencies of 46.8%, 6.4%, and 5.0% respectively in the group of normal subjects.