The major serum inhibitor of proteolytic enzymes is the α1-globulin, α1-antitrypsin. Hereditary deficiency of this protein is immediately recognizable on inspection of stained serum electrophoretic strips (agarose, agar, and cellulose acetate, as well as paper) in that the normal α1 band is absent (Fig. 1). Although the protein concentration of the α1-globulin zone is usually subnormal in deficient sera, it is not always so; and, the ultimate criterion for the establishment of the diagnosis must be made by genetic typing, as will be shown. Almost coincidental with the discovery of α1-antitrypsin deficiency by Laurell and Eriksson,1 in Sweden, was their observation that many persons with this abnormality had early onset chronic obstructive lung disease.