Phospholipids extracted with hot methanol from Mycobacterium tuberculosis, strain H37Rv, were fractionated with solvent mixtures and by partition chromatography on silica-gel columns. Of 12 components detected on a thin-layer chromatogram of the total phospholipid fraction, 6 components were purified. They were all phosphatidylinositol oligomannosides: two hexamannosides (H-2 and H-3), one tetramannoside (H-4), one trimannoside (H-5), and two dimannosides (H-6 and H-7). The molar ratios of fatty acid to phosphorus were 3 for H-2, H-4, H-5, and H-6, and 4 for H-3 and H-7. In each lipid, more than 80% of the total fatty acids were palmitic and tuberculostearic acids. Each of the six lipids had serological activity to various degrees.