In this issue of the Biochemical Journal, Robbe et al. have employed a state-of-the-art MS technique to re-examine the sweet and sticky sugar covering of human intestinal mucosa. The availability of highly sensitive MS methods has been instrumental in determining the complex structures of mucin oligosaccharides, and in demonstrating that there are variations in structure along the sections of the gut. In contrast to previous studies, these results described by Robbe et al. show some correlation with the activities of enzymes synthesizing mucin oligosaccharides in the human colon. Many questions still remain to be answered: for example, regarding the regulation of the relative amounts of sugar chains in individual mucins, and their roles in the homoeostasis of the intestinal mucosa. Structural studies are a solid basis for understanding the functions of sugar chains, and the mechanisms and significance of changes during the development of intestinal disease.