The variant surface glycoprotein (VSG) of Trypanosoma brucei is covalently linked to a phosphatidylinositol-containing glycolipid which serves as a membrane anchor. We previously identified a molecule, glycolipid A, which appears to be a biosynthetic precursor to the anchor [9]. In this paper we describe a related molecule, glycolipid C, which is similar to glycolipid A but which is more hydrophobic. Chromatographic analyses indicate that the polar head groups in glycolipids A and C are similar or identical. Both glycolipids contain phosphatidylinositol, but the inositol in glycolipid C is modified by a hydrophobic moiety. Since treatment of glycolipid C with mild alkali results in partial conversion to a molecule chromatographically identical to glycolipid A, it is likely that glycolipid C has an alkali-sensitive hydrophobic group, such as a fatty acid, linked to its inositol moiety.