Summary Mucopolysaccharides were isolated from whole human aortae and characterized by analysis, enzymatic digestion, optical rotation and I.R. spectroscopy. Average age of the groups ranged from 21 to 72 years. Total MPS and galactosamine/glucosamine ratios showed no significant change with age. Of the 4 MPS fractions identified, hyaluronate and ChS-C decreased with age while ChS-B and heparitin sulfate increased. The data are discussed in relation to age changes in other tissues of mesodermal origin. It is assumed that the complex pattern of human aorta is the resultant of age changes per se superimposed on degenerative and reparative processes. We wish to thank the Dept. of Pathology for their cooperation in obtaining aorta.