A few weeks ago, many of our friends suffered from ‘winter vomiting disease’, a form of gastroenteritis that swept epidemically across Germany. This unpleasant disease is caused by the highly contagious norovirus, a member of the Caliciviridae family of RNA viruses. Caliciviruses are unusual because they dock to sugar residues on the surfaces of cells to be invaded, rather than to proteins. The chemical details of this process were unknown, but reporting in the Journal of the American Chemical Society, Rademacher et al.1 present a nuclear magnetic resonance (NMR) study that determines which sugar residues are involved in the binding of another calicivirus, rabbit haemorrhagic disease virus (RHDV), to cells. Their technique could be used to develop drugs that block the entry of viruses into cells.