This update covers the literature for 2002 and 2003 dealing with the main topic of the previous review entitled Heterocyclic nucleosides. Chemical synthesis and biological properties and published in Curr. Med. Chem.-AIA, 2002, 1, 389. As in the first review, the papers in this survey are grouped by the type of the heterocyclic system that acts as a spacer between the hydroxymethyl group and the base moiety.