Intestinal mucins are glycoproteins containing a very high proportion of carbohydrate, up to 90%, and they can occur either in a membrane-bound or a soluble form (1). The general structure of these molecules includes discrete C-terminal and N-terminal regions, which are relatively poorly glycosylated, at either end of a long repeating structure, up to 50 repeats, which is heavily O-glycosylated on serine and threonine residues the first sugar in each oligosaccharide always being N-acetyl-galactosamine (2). These oligosaccharide chains can vary between 1 and about 15 saccharides. The C- and N-terminal regions are likely to be of importance in determining the membranous or secreted nature of the molecule (2).