From a nonpolar lipid fraction of Mycobacterium avium--Mycobacterium intracellulare complex cell mass, a new glycolipid was obtained, which was shown to be 5-mycoloyl-beta-arabinofuranosyl-(1-->2)-5-mycoloyl-alpha-ar abinofuranosyl- (1-->1')-glycerol. When examined by TLC, all the 12 strains of this species tested, including clinical isolates, were found to contain this glycolipid. But the glycolipid was not detected in Mycobacterium bovis BCG or Mycobacterium tubrculosis H37Rv.