Syndecans function as membrane receptors for a bewildering array of ligands through their glycosaminoglycan chains but their precise roles have been hard to pin down. Syndecans have previously been considered as ligand gatherers, working as co-receptors in collaboration with signalling receptors, but their potential to signal independently is now clear. New structural features of syndecan cytoplasmic domains have been described, together with new insights into signalling across the cell membrane that might involve the concentration of ligands in membrane microdomains.