Preliminary results of amino acid analysis of corium collagen from degraded historical leather, new leather tanned in various ways, untanned material, and new leather subjected to accelerated aging have shown that historical and aged leather are characterized by an altered amino acid composition, by formation of new amino acids, and by large amounts of ammonia. Based on the content of the amino acids glutamic acid, proline, tyrosine, histidine and lysine, the material can be classified as respectively new and historical by means of variance-covariance analysis. -- AATA