SummaryAlpha-l-antitrypsin (α1 AT) is a plasma protein with a protease enzyme inhibitory capacity; its synthesis is genetically determined. Some diseases are characterised by a low serum concentration ofα1 AT of abnormal biochemical structure. Such a deficiency may be associated in childhood with cirrhosis of the liver following neonatal hepatitis and in the adult with lung and liver disease.A case of an homozygousα1 AT deficiency in an adult with emphysema and cirrhosis associated with hacmochromatosis is presented.