Mucin glycoproteins are an important 'nonspecific' host defense at the interface of mucosal surface and lumen. However insights into structural and functional features of these enormously complex and heterogeneous glycoproteins have been markedly limited. In recent studies, the presence of several distinct colonic mucin glycoproteins has been demonstrated and their oligosaccharide side chains extensively characterized through conventional structural analysis and utilization of monoclonal antibodies. Glycoprotein diversity has been found to arise from previously unrecognized functional heterogeneity of colonic goblet cells. Rates of biosynthesis and secretion of different HCM glycoproteins appear to vary. In addition, a selective reduction in HCM glycoprotein IV has been demonstrated in specific association with ulcerative colitis. Finally preliminary studies suggest that additional alterations in colonic glycoconjugates may be present in ulcerative colitis mucosa.