Abstract Homogenates of human tracheobronchial tissue catalyzed the transfer of sialic acid, galactose, fucose and N-acetylgalactosamine to glycoproteins sequentially treated with the appropriate glycosidases. The optimal assay conditions and kinetic properties of these enzymes were determined using normal tissue. Since an abnormality in the biosynthesis of glycoproteins has been suspected in the pathogenesis of chronic obstructive lung diseases, the levels of these enzymes were determined in homogenates of human respiratory tissue obtained at necropsy from subjects with hypersecretion of mucus. The histological examination of the tracheobronchial tissue from diseased subjects ( n = 20) revealed the hypertrophy of mucous glands and hyperplasia of goblet cells. The enzymatic assays demonstrated that, in the diseased group, there was a twofold increase in the level of the activity of both a sialyltransferase (NAN to GalNAc) and a galactosyltransferase (Gal to GlcNAc), a threefold increase in the activity of both an N-acetylgalactosaminyltransferase (GalNac to protein) and a galactosyltransferase (Gal to GalNAc), and a fourfold increase in the activity of a fucosyltransferase (Fuc to GlcNAc) as compared to the levels in tissue from normal subjects ( n = 11). It appears that the hypersecretory states in humans may be associated with the synthesis of either abnormal glycoproteins or abnormal proportions of the usual glycoproteins.