The human chromosomal alpha 1-antitrypsin gene has been cloned. This gene is approximately 5 kilobase pairs long and contains three intervening sequences in the peptide-coding region. DNA sequences coding for the amino and carboxyl termini of a alpha 1-antitrypsin have been identified. Human alpha 1-antitrypsin and chicken ovalbumin show significant sequences homology and belong to a common protein super-family. Yet the number, position and size of intervening sequences reveal that the two genes are dissimilar.