The two most common hereditary lung disorders in Caucasians, alpha 1-antitrypsin (alpha 1-AT) deficiency and cystic fibrosis, have their major clinical manifestations in the lung. Rapid advances in biotechnology have resulted in a variety of gene therapy strategies for the potential treatment of these disorders. Three vector systems--plasmid, retrovirus, and adenovirus--have been evaluated for their possible utility in transferring genes in a fashion that would either alter the milieu of the lung or directly alter the genetic program of lung parenchymal cells. Two general strategies can be used: ex vivo modification of autologous cells with subsequent transplantation to the patient and in vivo modification with an appropriate vector containing the exogenous gene. Studies carried out in experimental animals show that it is theoretically possible to treat both alpha 1-AT deficiency and cystic fibrosis with gene therapy if the safety hurdles can be overcome to minimize the risks involved.