Polymethylated polysaccharides (PMPSs), glycans composed of 10–20 carbohydrate residues the majority of which carry a single methyl group, are produced by some mycobacterial species. O-Methylation thus occurs on 20–30% of all the hydroxyl groups within the molecule, rendering them amphiphilic. A property of PMPSs is their ability to form high-affinity complexes with fatty acids and their derivatives, suggesting a role in mycobacterial fatty acid biosynthesis. However, direct evidence for their in vivo function is still lacking. Over the past several decades the lipid-binding properties, biosynthesis, and chemical synthesis of PMPSs have been explored and this review will provide an overview of progress made in these areas. © 2013 Wiley Periodicals, Inc. Biopolymers 99: 697–712, 2013.